Goodman Hi Efficiency furnace with AC. Model CAPF3636CBA, won't heat or cool


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Old 09-20-14, 10:16 AM
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Goodman Hi Efficiency furnace with AC. Model CAPF3636CBA, won't heat or cool

Searches on this model number gets "no results found"
The furnace recently had a new board installed. The air circulating blower motor can be made to run but, we can't get heat or a/c. The red LED on board will give a quick blink when power is first turned on. The service man won't answer his phone, we thought there should be some kind of warranty on the board? The problem must be that serviceman is afraid of my Dog, the Dog is not mean at all! Serviceman made a big deal about the Dog, so the Dog was locked outside, but still. he must be afraid of all Dogs, Most people have Dogs today, so he is in the wrong kind of business? (Its a ridiculous situation!)
Back to the furnace problem, any hints as to what the problem is. The first thing I am thinking to try is to start with the Thermostat, even though it is not that old. Seem like a good idea? (I am new to furnaces with printed circuit boards.)
 
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Old 09-20-14, 10:26 AM
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Here is a link to some information about the Goodman CAPF cooling coil: http://www.alpinehomeair.com/related...4%203.2014.pdf

To better assist you please post the model number of your furnace and thermostat. Photos of your control board wiring and thermostat wiring would be very helpful, if possible.

For starters, look on the control board for an automotive type fuse (purple or amber) to see if it is blown. If it is you will not have 24V to control your system.
 
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Old 09-21-14, 06:31 AM
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Hi Firedawg,
Thanks for the reply and help. The Control board is somewhat different in our furnace. I WILL take pictures of the board and thermo. The house is one my brother and I bought, he lives in it, and its 50 miles from me. I am going there today. The model number is the model number I put in the subject line and the one I got "no results found" when I did a search on it. I printed out page 68 from the PDF of the service manual you sent, thanks a lot for that, I put the PDF on a USB drive to take with me.
I am the one that put the new thermostat in last year and it was working for a year. It could have gone bad, and he doesn't like it anyhow, so it will get checked. I am an old electrician, and I have a few decades of electrical and instrumentation design experience, so with your help, I think we can figure this out. The model number again is: CAPF3636C6BA and the serial number is: D807094324, I got these off the label on the furnace, of course. I will get back on here when I get back.
Thanks again
 
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Old 09-21-14, 08:04 AM
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The photo of the control board was just to show you an example of where you would look for the 3 or 5 amp fuse. The model you provided is the a/c coil not the furnace section. When you arrive at the location you can look inside the unit and find the data plate that will contain the model number. We will need that model number to better assist you.
 
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Old 09-22-14, 05:27 AM
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The model no. is:GMH950904CXAC, serial no.is 0809438351

Hi Firedawg,
I eventually found the model number of the furnace inside, with a good flashlight. (It was easy to miss, the first time.) I questioned my brother Sam about WHEN this unit quit working. It was the AC that stopped working back in June/July. This happened less than a week after the service man installed a new Control board. Sam had a couple of window ac units so he installed them temporarily but that quickly ran into months. He never thought to check the furnace for heat, until lately. About a month ago I took a look at it and checked the fuse then, it was OK and it still is OK, its a 3 amp.

I got some numbers off the control board: 0914N290349, 1165-410, PCBBF132, but I don't know what they really represent.

The Honeywell Thermostat was assembled incorrectly, when my brother installed new batteries. You need to put he AAA batteries in last, after snapping the assembly together, but correcting that was NOT the problem. Having the Thermo back on the wall or removed makes no difference to what the furnace does.

If you turn the utility box switch on, you get 1 red LED flash and after maybe 30 seconds the furnace blower starts and continues to run. I had the access panels off to watch and nothing else happens. Of course I held the door switch closed to be able to watch and see that nothing else happens. The small fan for the heat exhaust never runs either. There is AC voltage into and out of the transformer, so I did check that.

Inside the access panel, there is a list of trouble codes as you know. Number 1 code for 1 flash says ; Locked out, number of tries exceeded. (Might be paraphrased.) I looked to see if something needed reset? what does this code mean?

I wonder if this Control board is shot already? Do they typically have some kind of warranty.

( The serviceman knows my brother's phone number and won't even answer the call. I am thinking about calling him to see if I can talk to him?
At one time I repaired appliances also, they were NOT loaded with electronics, and we never acted like this guy with customers.)

The photos didn't turn out that great, one of the board is somewhat OK and one of the Thermostat, a simple two button deal with a small window for a display is about all that is visible. I will see if I can add them to this post

Thanks Again.
 
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Old 09-22-14, 07:47 AM
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Thanks for the model number. I am sorry to hear you weren't able to get the system up and running. Did the a/c work after you got the issue with the thermostat batteries resolved? The a/c issue should be a separate issue from the furnace. When the repairman installed the new control board was the furnace and a/c both operating properly before he left? I am thinking perhaps the thermostat is the issue and not controlling the system. Did you try to jump from R to W on the control board to see if the furnace would start? Here is a link to a manual for the furnace that has a trouble-shooting guide and wiring schematics: http://www.alpinehomeair.com/related...R%205.2013.pdf

Did the 1 flash LED go back to a solid LED after it was reset? Based on your description of what is going on, it sounds like a pressure switch not closing. But, that should produce a flash code (unless it is a bad control board). These type of furnaces pressure switches are very sensitive and won't allow the furnace to start up unless everything is just right including the vent is open, the combustion air pipe is open, condensate pipe not clogged, etc.

I would start with jumping R and W at the control board to bypass the thermostat to see if the furnace will start up. You can do the same for the a/c by jumping R and Y to see if the condenser will come on. To get the blower to come on also you will also need the G wire to the equation.

As far as the thermostat; was it set-up to operate a furnace and a/c? If the thermostat is not properly set up for the particular system it is supposed to operate it will not function properly. Since you said the thermostat was installed not that long ago I have a feeling the answer may lie there.

If jumping the wires doesn't get the system going (which points to the thermostat) then further trouble-shooting can be done. It could also be a tripped auxiliary limit switch which often results from a dirty air filter. That switch requires a manual reset.
 

Last edited by firedawgsatx; 09-22-14 at 09:04 AM.
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Old 09-22-14, 12:17 PM
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When I got back to the office I had a little more time to think about your issue. If I recall correctly, that furnace will start the blower when on lockout mode. When I get a chance I will verify that in my technical literature.

When troubleshooting I like to start with the simple and obvious things:

1. Is the thermostat receiving 24V from the furnace transformer? That can be easily tested with your meter.

2. If calling for heat is the thermostat set to a temperature well above the room temperature. The same goes for a/c except making sure the thermostat is set well below room temperature.

Question: Did you remember to set temperature well above room temp when calling for heat? People forget this step. In the summer they just flip it to heat and expect it to come on when the room temperature is 78 degrees and the 'stat is set to 68.

If the inducer motor does not start it could be because the pressure switch is closed. When a call for heat is made modern control boards look for the pressure switch to be open. If not, the inducer motor will not start up.

Another thing is that furnaces of the type you are working on have a 2" or 3" pvc vent pipe and sometimes a 2" or 3" pvc combustion air pipe. Some have screens on the end of the pipe that can get clogged. Other times bees, birds, critters or debris of some sort clog up the pipe and cause issues. So make sure the pipes are clear of obstructions and screens (if present) are clear.

90% furnaces are efficient because they are condensing and remove a lot of water out of the hot gases. This water has to be collected and removed through a drain pipe. If anywhere in the drain system is clogged it can cause operational issues.

So, it is important to ensure the vent and combustion pipes are clear as well as the condensate drain system is clear and not backed up.

You stated the inducer motor did not start. That could be due to a bad inducer motor. You could check for voltage on the control board to see if you are getting 120V where the motor leads connect.
If you are getting 120V on those terminals when calling for heat it would point to a bad motor and require replacement.

I am just throwing out some ideas where to start troubleshooting. once we get your feedback we can get into a more targeted approach.

Here is a link to some information about the control board: http://www.emersonclimate.com/docume.../0037-7474.pdf
 

Last edited by firedawgsatx; 09-22-14 at 12:42 PM.
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Old 09-22-14, 06:01 PM
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I printed the troubleshooting pages, 42 and 43 of the furnace document. I put all three documents on a thumb drive to take with me, Having the documents with your help, I will get this furnace working. To answer your questions, probably not in order, I did not jumper any of the thermo wires connected to the control board because I didn't remember what the colors to jump were. I will do that at the thermo after checking that the colored wires are in the right place and check the power to the thermo also, that was a good suggestion. I will take test clips and other stuff I need next time. Then I will jumper the terminals on the control board to see if I can get heat and cooling. I still think the thermostat could be bad as you suggested. Its going to be back to the basics from step one as you suggest, so I will take the thread printout and use it as a check list to make sure I don't miss a step. Yes I did remember to turn up the thermo all the way (90 degrees) when calling for heat. This furnace did heat last winter after I installed the thermostat. Then it worked for AC in the string. After the serviceman installed the new control board, the AC worked for about a week, then it quit. I don't think my brother even thought to check that the furnace could produce heat. I have worked on older furnaces, but not these hi-efficiency ones, but it had to come sometimes I suppose, and I have a Trane 90 some percent system at home. The furnace manual document is going to be a big help, so thanks for all three of them. I'll be going back to it, probably tomorrow. The single flash and the furnace being "locked out" and causing the furnace blower to run, seemingly for no reason, is new for me and had me stumped. Thanks again for the help.
 
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Old 09-22-14, 06:16 PM
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One reason that the inducer motor won't start when there is a call for heat is a closed pressure switch. When there is a call for heat, the control board checks to see if the pressure switch is open. If it is closed, the sequence stops and, after a short time, the pressure problem code is displayed. If you get a pressure switch code, and the inducer will not come on, remove one of the wires from the pressure switch. If the inducer comes on, the pressure switch is stuck closed. Tapping lightly on the pressure switch body may open the switch and the unit may start. I have attached photos of what the pressure switch looks like. The GMH95 has two pressure switches/

When you set the thermostat to call for heat make sure you look at the LED on the control board and observe the flash code.

Yes, these newer furnaces can be a bear to troubleshoot. The flash codes will normally point to a possible cause but don't provide a code for every issue such as if the condensate drain is backed up. Those condensate issues can create a lot of problems.
 
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Old 09-22-14, 08:35 PM
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I see you added pictures of the pressure switches, that will help. Thanks, now I am beginning to think with all of your help, I will be able to get this furnace working. I am taking copies of this information with me. Now I can get into figuring this out.

Thanks again, and of course I will let you know what happens.
 
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Old 09-24-14, 07:34 AM
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I think I found major problems. Now to keep my findings from getting complicated. I used your email as a check list and I double checked everything. The 3" outside PVC lines were clear. Jumping the R and W wires to get heat did nothing. The same trying to start the AC unit. Then I checked the pressure switch, with the AC power off of course for all continuity checking, the pressure switch which is supposed to be normally open, was reading closed, SO I pulled the wires off the switch and tested the switch, out of the circuit, and it is normally open.
Something like this can get you going around in circles, so started with the diagram on page 4 from White Rodgers and decided to check everything I could. turned the AC power back on and checked the 24 volt AC transformer, and it was putting power to the control board. Then with AC off again, I checked the Hi limit and Aux limit circuit, two normally closed switches in series connected to HLO and HLI, and that was correct.
Using my Ohmmeter, with power off, I checked the Igniter, the Rollout switch, and I wasn't finding anything wrong so far. Looking the diagram, "I might as well" check the Gas valve. It has 3 wires, a MV com, MV LO, and MV HI. This Gas valve has to be the 2 stage version, and with its connector OFF, I get no continuity. This Gas valve draws .430 amps so I am sure it should show some continuity resistance. (I didn't think to reverse the leads of the meter in case there is diodes or something inside the gas valve preventing a continuity check, (and it runs on AC).) I would be tempted to put 24 volts directly on the Gas valve terminals for a second to see if it would open, because it will be a bear to change it, but doing this is not to be taken lightly, but again there is a Gas shut off handy).

(There is NO union of the gas line and the drip Tee and nipple to collect possible dirt coming in with the gas is Not assembled correctly. The original furnace installers definitely installed the gas line the hard way. I know because my Dad was a plumber and I learned from him.)

I had no hope of getting heat out of this by then. Back to getting the AC unit to start. Jumping the terminals did nothing. This kind of a situation get you thinking. I removed the red and white wires that control the AC unit from the control board. Then holding the door switch closed, because this is the only way the 24 volts gets to the control board, I connected my meter on the AC scale to the control board terminals to make sure I was getting 24 volts, THEN, with the meter showing 24 volts I manually held the red and white wires for the AC unit on with the meter, AND the 24 volts dropped to nothing. The 24 volts would not hold up under a load. Hmmmm at this point, the new control board must be bad. (I went for a cup of coffee.)

Then I decided to put the red and white control cable for the AC unit directly on the 24 volt output of the transformer. (I knew that if I mistakenly connected to the 120 volt side of the transformer, that would be very bad for the contactor in the AC unit.) This would test the transformer under load also, and FINALLY a positive result, the AC unit ran.

Now some questions, about the gas valve, it operates on 24 VAC, so I don't think a volt ohm meter with a 9 volt battery to test it would destroy the Gas vale?? But If the 120 volts on the control board was outputted to the Gas valve somehow, I am sure 120 volts would fry it, agree?

I have come to the conclusion that the new Control board is bad, agree? Now, assuming I need to replace the gas valve, and I will correct the gas line hook up, of course. With a new Control board, I will be concerned about ruining another Control board, BECAUSE I really don't know what caused this whole scenario to happen in the first place. Have you ever run into anything like this?

This is really getting to be an experience with my first Hi efficiency furnace servicing. Can you make anything out of all of this?
 
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Old 09-24-14, 08:23 AM
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Sorry to hear you still are having trouble getting the system operational. It is difficult to troubleshoot when both the a/c and furnace are not working. Are they both non-operational because of a control problem or because of separate issues. That is the question that has to be answered. As long as the control board is sending the 24V to the R terminal and the Y terminal is jumped to R the condenser outside should come on.

Before you started troubleshooting:

Did you check the LED on the control board to see if it was not flashing? It needs to be a solid light for it to be in normal status. If it is still in lock-out (1 flash) it needs to be cleared by turning off breaker for 30 seconds and turning breaker back on.

Did you test for 24V between R and C at the control board?
Did you check for 24V between the #3 and #6 wires on the 12-pin connector?

The first thing that should happen after the call is made for heat is that the inducer motor should start up. If that doesn't happen you need to see if voltage is being sent to the inducer motor on the control board. The black lead from the inducer motor should go to a 2-pin connector and the white wire should go to the IND-N terminal. When calling for heat there should be 120V across those two terminals.

Does the system have a condensate safety switch installed? If so, possibly the switch activated and shut down the system. As I stated in an earlier post, condensate drainage issues can cause a lot of issues with high efficiency furnaces.

When you connect the red and white wires from the condenser directly to the transformer and it fires up it would seem to be a bad control board if it was not getting voltage to the terminals. But you indicated the meter showed voltage to the terminals.

Remember, a meter measures a difference in voltage. If the thermostat is "off", you should read 24 volts between R and Y on the control board. When the thermostat is calling for cooling, you will read 0 volts between R and Y on the control board. You will also read 24 volts from Y to C when its calling for cooling.

Does the furnace have two pressure switches? If so, did you check both? You stated that the one pressure switch you checked showed it to be closed. If it is closed the furnace will not start because when a call for heat is made the control board is looking for an open pressure switch. If it sees it is not open the furnace will not start the inducer motor. When that happens you can remove one of the wires from the pressure switch and see if the inducer will start.

You can remove the black hose from the pressure switch and gently suck and blow to hear if it makes a "click". Also make sure the bleed port (where the black hoses attaches) is clear. It can get crud in there and get blocked or restricted so the pressure switch will not operate. The best thing I've found to use to clear the crud out is a very small drill bit. The port needs to be clear all the way through. Also make sure the hoses do not have any water in them.

At this point I definitely cannot agree the control board is bad.
 

Last edited by firedawgsatx; 09-24-14 at 10:19 AM.
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Old 09-24-14, 11:56 AM
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These answers to follow your questions in order

The LED never did anything except flash once when the power is turned on. (It NEVER stays on to be in normal status as you say, but the blower always runs and will eventually shut itself off.)

I did check for 24 volts on these terminals, but I don't remember exactly as you are asking, but there definitely was 24 volts there.

I didn't think to check for 24 volts on the 12 pin connector between the #3 and #6 pins, so I didn't specifically do that.

No, I didn't check for 120 volts at IND and IND-N. I got away from looking at the inducer motor after I found the Gas Valve had no continuity through either side, but I did check the continuity of the inducer motor windings themselves and it has continuity and low OHMs as typical for a motor. I thought to do that, in case the motor is thermally protected with a thermal fuse, (which are located under the covering of the windings). I would guess the Inducer motor is OK, but time will tell.

I had to clean the condensate pump and reservoir last year because the installer dropped a screw into it and that caused a rusty water mess, and I don't remember it having an interlock safety switch. I didn't really search for one this time, but I will my brother look at it, again.

I don't Remember exactly what readings reading I was getting on each set of terminals as you are asking with this question, but I do know I couldn't get the voltage on the control board on Y,W,R,G, & C to do anything, and that is why I hooked the two conductor red and white cable from the AC condenser directly to the 24 volts of the transformer to see if the AC condenser would run and as I said in my post this worked, the condenser started and ran.

The furnace has one pressure switch. I tested without the wires connected after I initially got a close contact reading, and the pressure switch then the swich showed normally open as it should. I do think I tried to start the furnace with one wire off the pressure switch and just got the 1 flash while the blower motor ran again. This is the switch in the right of the photo you sent. T switch that looks the same on the left has a hose connected, I think it is at the bottom of the A coil?, I know it goes down in there somewhere. Maybe I remember this wrong, but I think it is the High Limit N.C. switch in series with the AUX Limit switch connected to HLO and HLI and these two switches show normally closed as on the diagram.

For your last question, when the continuity check on the switches came out right, it didn't occur to me to check the hoses as you described, but the switches look pretty clean.

You didn't mention anything about my finding on the continuity of the gas valve. Now I am wondering exactly what OHMs scale I was using. Since these gas Valves don't draw much current, it could be that I used too low of an OHMs scale on the Digital meter. I will try my trusty Analog meter next and I sure hope the Gas valve is O.K.

I almost forgot one question, I did try turning OFF the power to try and reset the system several times and I also tried the RESET button on the control board.

I sure hope you are right about it not being the control board but earlier in the year the AC system was working as wired with this control board in there, and the same Thermostat was working as well. I don't live there, and my brother doesn't remember if the heat would come on when the AC quit. (He is a contractor himself and running himself crazy with this economy.)
 
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Old 09-24-14, 01:54 PM
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The LED never did anything except flash once when the power is turned on.
When you say flash once do you mean it continues to flash once every couple of seconds or only just blinks one time period never to blink again?

It NEVER stays on to be in normal status as you say, but the blower always runs and will eventually shut itself off.)
According to the schematic you should have two pressure switches; one for the inducer motor and one for the front cover.

This furnace turns the blower on when it is in lockout. I assume the blower is operating until it self re-sets after one hour or the power is interrupted.

If the R terminal is getting power and Y terminal is jumped the condenser should start up immediately. So it would appear your primary problem is getting power to the R terminal.

There should be 24V across R and C at the terminal board. Without that nothing else is going to happen. If you test at pins 3 and 6 on the transformer side 12-pin plug and you get 24V and you do not get 24V to R and C terminals you either have a blown fuse or a bad control board. That is what I would test, first chance.

When R is jumped to W at the terminal board the inducer should start up immediately. As stated in an earlier post, if the pressure switch is not open then the control board will not let it start up. The control board also checks to see if the safety devices such as rollout switches, limit switches and etc. are open/closed. Did you check all of the limit switches to make sure they weren't tripped?


You definitely have a head scratcher there. I am still not clear on whether the control board ever resets. Once the power is shut off and then turned back on the control board should have a solid LED light (normal status). I would not expect it to start blinking until a call for heat is made and it has a problem.

Here is a link to another manual that may assist in troubleshooting:

http://www.graycoolingman.com/upload...n_io-gmh95.pdf

On page 7 of the control board manual I linked in an earlier post it states that the blower is activated on lock-out. There is also a recall button that will show the last five faults. There is a fault reset button, as well. It may be worth a try to reset it.

I have to go out in the field now. I'll check back in later. Hopefully some of the resident experts will stop by and weigh in.
 

Last edited by firedawgsatx; 09-24-14 at 04:22 PM.
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Old 09-25-14, 09:42 AM
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I apologize for the delay. I will address your concern about the gas valve.

Looking the diagram, "I might as well" check the Gas valve. It has 3 wires, a MV com, MV LO, and MV HI. This Gas valve has to be the 2 stage version, and with its connector OFF, I get no continuity. This Gas valve draws .430 amps so I am sure it should show some continuity resistance. (I didn't think to reverse the leads of the meter in case there is diodes or something inside the gas valve preventing a continuity check, (and it runs on AC).) I would be tempted to put 24 volts directly on the Gas valve terminals for a second to see if it would open, because it will be a bear to change it, but doing this is not to be taken lightly, but again there is a Gas shut off handy).
The gas valve does have diodes so checking for continuity across the terminals is of no use. What type of gas valve does it have: Honeywell, White-Rodgers ???

You didn't mention anything about my finding on the continuity of the gas valve. Now I am wondering exactly what OHMs scale I was using. Since these gas Valves don't draw much current, it could be that I used too low of an OHMs scale on the Digital meter. I will try my trusty Analog meter next and I sure hope the Gas valve is O.K.
The best way to test a gas valve is to use a clamp ammeter, a voltmeter and a set of jumper wires. But to do that properly you have to get the inducer motor to start up. The only way the inducer will start on this furnace is if there is power at the circuit board terminals, R and W wires are energized and after the control board performs safety circuit checks. If it does not pass the safety circuit check due to an open limit, roll-out switch etc. the inducer will not start.

Here is a way to test a gas valve:

First test is for amp draw using a clamp ammeter. Set the ammeter to Amps AC.
Then clamp it around the 1st stage wire going to the gas valve. In your case that would be the gray wire. With the door switch pushed in and calling for heat the inducer should start up and the hot surface ignitor should start glowing. Shortly thereafter about a trial for ignition should start. At that point you should see an amp draw on the meter. If there is no ignition in 4-7 seconds the control board will cut off the 24V volts to the gas valve. If you get an amp draw that means the gas valve is energizing (power is going to it and something is pulling in (such as a solenoid). It also that means the control board is sending the signal. If you don’t get an amp draw that means the control board is bad or the gas valve solenoid is open.

If there is no amp draw you can use your multimeter to see if voltage is actually coming into the gas valve. There should be 24-28V going to the gas valve when there is a call for ignition. If not, then you are looking at a wiring problem or a control board issue.

To do this test remove the plug on the gas valve. Not all gas valves have plugs. Because it is a two-stage furnace you should have three wires going into the gas valve. The common wire (brown) is probably in the center of the plug and first stage wire (gray) is on one side and second stage wire (orange) on the other.

Some control boards look for continuity through the gas valve. If the gas valve plug is removed then the test won’t work. If that is the case on yours, you will have to keep the plug inserted into the gas valve and stick your meter probes in where the wires enter the plug.

Insert your black lead into the brown wire and the red lead into the gray wire side. Set meter to volts AC. Just as before: with the door switch pushed in and calling for heat the inducer should start up and the hot surface ignitor should start glowing. Shortly thereafter a trial for ignition should start. At that point you should see a reading of 24-28V on the meter. If there is no ignition in 4-7 seconds the control board will cut off the 24V volts to the gas valve.

For both tests you will only see the voltage for around 4 seconds so don't blink.

Here is another test you can do to test the gas valve. Do this for ONLY 1-2 seconds.


Turn off power. Remove wires or plug from gas valve. Use two jumper wires with connectors on both ends and connect one wire to the gas valve Common pin (middle) and the other end to the common terminal on the 24V side of the transformer. Connect the other jumper wire to where the gray wire connects at the gas valve plug and the other end to the "hot" terminal of the the low voltage side of the transformer. Turn power on by pushing switch and you should hear gas start coming out (do this for one to two seconds). If gas does not begin to flow you have a bad gas valve.

I would once again make sure the intake air and vent pipes are totally clear with no obstructions, make sure the condensate drains are not backed up, the bleed port on the inducer motor is clear (use drill bit or opened up paper clip, make sure the 3 amp fuse if good, make sure the hoses to the pressure switch(s) are clear all the way through, make sure the two auxiliary limit controls are not tripped (manually reset), make sure both roll out switches are manually reset and etc.

I say check the fuse because I have on a couple of occasions seen a fuse that looks good but is actually arcing. I have attached a photo of an arcing fuse.

Check for 24V across the R and C terminals at the control board. If you do not have the voltage there you will need to determine what is happening by checking line voltage, transformer input/output, check fuse, make sure 12-pin plug is fully seated and any wire connections that are spliced.
 
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Old 09-25-14, 01:40 PM
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I have attached a portion of the wiring diagram for the furnace you are working on. I color coded the low voltage wires so you can see how if any one of the safety circuit controls is not as it should be for normal operation it will lockout the furnace ignition sequence. Note how the two pressure switches have to be in the open position. Also the roll-out switches, auxiliary limit switches and primary limit control must all be in the closed position.

While furnaces basically operate the same, there are differences depending on the make/model as to the sequence of operation.

As stated in previous posts, the pressure switches are safety devices to prevent furnace operation if an unsafe condition exists. One pressure switch is to ensure the vent is not blocked (ID Blower Pressure Switch) shown in diagram. The other pressure switch (Front Cover Pressure Switch shown in diagram) is to ensure the condensate drain is not restricted or blocked.

I suggest that you remove the 12-pin plug on the control board and inspect it for any unusual signs such as moisture inside the plug or connector on the board, any wires that are protruding further than the others, any sign of oxidation and etc. Then re-insert the plug back into the receptacle on the board making sure it is fully seated. Looking at the diagram I attached it looks like the 24V goes through the two roll-out switches before going to the R terminal. I can't be sure of that though. I suggest you find the two roll-out switches and test for 24V on either side by testing from each terminal to ground. These are manual resets and can be reset by pushing the small button in the center of each switch.
 
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Old 09-25-14, 03:17 PM
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The LED never has done anything but give a real quick flash, once, if you blink you will miss it, and it doesn't look like it is at full brilliance. Its a one time flash, until the power is turned off or the door switch is released and pushed in again. I don't think the flash could be seen through the plastic peephole very well if at all.

It does have two switches as the photo you sent. I checked both, the one on the right is N.O., but until I removed the wires from it, it showed N.C. , (Which I guessed could be a stuck relay contact on the Board, Or?) The switch on the left showed N.C. I will check this again, is this the switch HIGH LIMIT in series with AUX. HIGH LIMIT, connected to HLO and HLI? If that is not the switch, I don't see another PRESSURE switch on the diagram.

You say there is two pressure switches, one for the inducer motor and one for the front cover. I need to look at that again, I saw the hoses but didn't completely know what pressure they were monitoring.

(I can see this system is somewhat like a power plant, and they call the inducer motor an induced draft fan, they have tall chimneys to get the draft going through, so maybe I can catch on to what is going on here?.)

The furnace motor eventually shuts off, yes, but it only takes no more than 15 minutes.

When I jumped the R and W wires the furnace never started to heat. I even pulled the Honeywell Thermostat from its back plate in case it was the problem. As you know the electronics and batteries all come off, and the only thing on the wall then, it the terminals with the wires connected to them, so then I jumped the R and W wires again and got no start up on the furnace. So then, I tried to see if the Condenser out side would start by jumping R to Y and that did nothing. Jumping R to Y gets one side of the line to the condenser, the red wire, I could see that, but the W wire from the condenser was connected to the Y terminal on the control board, that I know I needed for the condenser to get 24 volts, so I removed the condenser W wire from the Y terminal and held it onto the G terminal and nothing happened. By this time I was ready to quit, but I used my meter and there was 24 volts on the board terminals, so I left the meter connected and held the wires on to the same terminals and NOTHING happened again. I was really ready to quit, then I took the R and W wires for the Condenser off of the board terminals and held them right onto the terminals of the 24 volt transformer and the condenser started up. at least I now had one positive result and knew the transformer was holding up.

I made a sketch of how the 4 conductor Thermostat cable is connected on the board, BEFORE I removed the two wires for the condenser. The Yellow wire is on the Y term., the white wire is on the W term., the red wire is on the R term. and the green wire is on the G term. The condenser 2 conductor had its white wire on the Y term. and the red wire on the C term.

The thermostat has its wires on their corresponding terminals colors and at one time the thermostat worked, last winter, when I installed it.

To review this problem; for anyone looking at this thread, the furnace worked, then spring came and the AC was beginning to get used. The AC worked for a while then quit. A serviceman installed a new Control board and the AC worked again for about a week and the AC quit working and of course the condenser wasn't running. At this time the owner didn't think to check and see if the furnace would come on. The serviceman has quit on coming back, he says its the German Shepherds, but maybe he know something else? Who knows about people in this day and age? (The Dogs are not mean, you throw the ball for them and they will love you forever.)

I am going to check the control board terminals again for voltage on the right terminals. I am also going to recheck the limit switches as you say and the voltage on the 12 pin connector as you said earlier. I have printouts of everything. I need to start fresh on this.

I tied the reset button already. The gas valve is a Gemini brand and I am going to leave testing the gas valve to the last, its pretty hard to believe its bad, but this is a house built in 1927, we really need to add more insulation, this furnace has been worked hard.

I will follow the rest of your advice in the rest of this post, in case I need to test the gas valve, and I will retest the FUSE, but I am pretty sure I did use my ohmmeter on it and I had new ones but they are 5 amps, which I could still try.

Thanks a lot for hanging in there with me. I am going to check the link you sent now from gray cooling.
 
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Old 09-25-14, 05:43 PM
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It is beginning to sound like you have a bad wiring connection between the transformer and the control board. Hopefully when you check the 12-pin plug for corrosion and moisture and etc. it will reveal the issue. I also suggest you check the ground for the power coming in to the furnace and the ground for the control board. As you well know, a bad ground will cause all kinds of power issues. Now to address your post:

It does have two switches as the photo you sent. I checked both, the one on the right is N.O., but until I removed the wires from it, it showed N.C. , (Which I guessed could be a stuck relay contact on the Board, Or?) The switch on the left showed N.C. I will check this again, is this the switch HIGH LIMIT in series with AUX. HIGH LIMIT, connected to HLO and HLI? If that is not the switch, I don't see another PRESSURE switch on the diagram.
I have attached the diagram again with the two pressure switches outlined in red. The proper way to test a pressure switch is with a manometer but the average homeowner doesn't have one of those in his toolbox. As I suggested in an earlier post I suggest you make sure the black rubber hoses are clear end to end by blowing through them. Also make sure the port on the induction fan motor where the black hose attaches from the pressure switch is clean. Use a paper clip or small drill bit to ream it out until it is clear all the way through the port.

You say there is two pressure switches, one for the inducer motor and one for the front cover. I need to look at that again, I saw the hoses but didn't completely know what pressure they were monitoring.
Two-stage furnaces have two pressure switches. One is for the vent and one is for the condensate drain system. The one that attaches to the induction fan motor is for the vent. Just follow the black hoses and it will become clear.

(I can see this system is somewhat like a power plant, and they call the inducer motor an induced draft fan, they have tall chimneys to get the draft going through, so maybe I can catch on to what is going on here?.)
The vent pipe (pvc pipe right side) is for the exhaust gases. This is the pipe that the pressure switch has to prove is open. If it is partially blocked by a birds's nest or etc. the pressure switch will not close when the induction motor starts.

The furnace motor eventually shuts off, yes, but it only takes no more than 15 minutes.
This is where I get confused. If there is no power to the R and w terminals how is the motor running? Can you expound on what you were talking about as far as the 15 minutes?

I made a sketch of how the 4 conductor Thermostat cable is connected on the board, BEFORE I removed the two wires for the condenser. The Yellow wire is on the Y term., the white wire is on the W term., the red wire is on the R term. and the green wire is on the G term. The condenser 2 conductor had its white wire on the Y term. and the red wire on the C term.
The wiring appears to be correct.

When I jumped the R and W wires the furnace never started to heat.
When you jumped R and W at the furnace did the inducer draft motor start to run? Did you test for 24V between R and C at the furnace?

Jumping R to Y gets one side of the line to the condenser, the red wire, I could see that, but the W wire from the condenser was connected to the Y terminal on the control board, that I know I needed for the condenser to get 24 volts, so I removed the condenser W wire from the Y terminal and held it onto the G terminal and nothing happened.
Here I am confused again. Here is the way it works. Jumping R to Y (white wire) sends 24V to one side of the contactor. Jumping R to C (red wire) provides the common to the other side of the contactor. Holding G to the white wire on the Y terminal would do nothing as the G terminal is not powered until the thermostat sends 24V to it.

The condenser 2 conductor had its white wire on the Y term. and the red wire on the C term.
That will work.

By this time I was ready to quit, but I used my meter and there was 24 volts on the board terminals, so I left the meter connected and held the wires on to the same terminals and NOTHING happened again.
This is where I get confused again. Did you have the white wire on the Y terminal and the red wire on the C terminal and then jumper from R to Y?

The gas valve is a Gemini brand and I am going to leave testing the gas valve to the last, its pretty hard to believe its bad.
Gas valves rarely go bad. I really don't think that is your problem.
 
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Old 09-26-14, 09:36 AM
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I printed your last post, and now with the schematic you are showing me, and the questions you are asking in this post for me to really check on, I think I will have a very good chance to get it fixed tomorrow. I am going there tomorrow.

I will check for a bad connection between the transformer and the control board to be sure, but I already know the 12 pin plug looked pretty clean, I did have it off while checking connections, but its possible to miss something the first time.

The red outlined switches will really help to make sure I am looking in the right place, thanks for that.
I wasn't talking about this schematic not showing a second switch that I wasn't sure about, the diagram I had then was sheet 4 of the White Rogers PDF. This schematic is going to be a great help. By the way I know the wiring for something like this is complicated, but the schematic is different in the way they show it, compared to what I have seen and done in engineering. At least a few labels as to what section a viewer is looking at would help. Being familiar with the appliance, as you are sure helps to understand the drawing, ideally it would be better if drawings were clearer to understand a system on their own, but where I worked wasn't always perfect either. Your help is greatly appreciated and I feel guilty about taking up so much of your time.

I WILL really check those pressure switches as you suggest in this post.

I checked the PVC pipes as far as I could see, but I am going to take some polyethylene tubing with me to fish further into the pipes, this time.

The motor that never ran for more that 15 minutes is the furnace blower, I NEVER saw the Inducer motor turn, except by my hand and if felt very smooth, its not a motor bearing problem, but I wondered if it still needs lubricated once in a while, they ARE open frame motors, my Trane has one similar, I think I remember.

About your questions on the voltages on the control board terminals, right now I wouldn't make any bets that I didn't confuse myself. I will recheck them for sure.

I will start at the beginning and systematically recheck everything with a fresh attitude, and I will get back on here and tell you the results.

Thanks again for the help and maybe this thread will help others to see what is involved with servicing these Hi efficiency furnaces, which are great when they are working and easy to take for granted.
 
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Old 09-26-14, 11:02 AM
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I will check for a bad connection between the transformer and the control board to be sure, but I already know the 12 pin plug looked pretty clean, I did have it off while checking connections, but its possible to miss something the first time.
As it appears you are losing voltage between the transformer and the R and C terminals I would check for voltage between pins 3 and 6 on the 12-pin plug. It will be an orange wire top corner with gray wire directly below.

I wasn't talking about this schematic not showing a second switch that I wasn't sure about, the diagram I had then was sheet 4 of the White Rogers PDF. By the way I know the wiring for something like this is complicated, but the schematic is different in the way they show it, compared to what I have seen and done in engineering.
As it says at the top of the diagram it is showing a "typical" application. These control boards are used on many different furnaces. So, it is necessary to use the wiring schematic for the exact wiring.

I checked the PVC pipes as far as I could see, but I am going to take some polyethylene tubing with me to fish further into the pipes, this time.
When the inducer draft fan starts the pressure switch will not close if the vent pipe is blocked. This is a safety feature. You can also take the pvc pipe loose where it exits the cabinet and look up in there. A plumbing snake is a useful item to run through the pipe if you have a long run. A lot of times installers do not pitch the pipe back towards the furnace or there is a sag in the pipe and water collects in the low spot which of course restricts flow of exhaust gases.
Of course, the combustion air intake needs to be clear and can be taken off to inspect it. Hopefully it wasn't glued.

The motor that never ran for more that 15 minutes is the furnace blower, I NEVER saw the Inducer motor turn.
Ok, I understand. Of course, until you can get 24V to the R and C terminals at the control board and then jump R and W the inducer fan will not come on. On a call for heat when jumping R and W terminals the inducer should start up. The inducer should be getting 120V from the IND and IND-N terminals on the control board. If an inducer motor does not start sometimes it will get very hot to the touch.

But as I have said if the control board sees that the pressure switch that is NO is closed it will not let the ignition sequence start as a built in safety. I hope that by inspecting the pressure switch and ensuring the hose is not full of water, no crud in the hose or the port on the motor that condition will clear.

I will start at the beginning and systematically recheck everything with a fresh attitude, and I will get back on here and tell you the results.
That is sometimes the best thing to do. Walk away for awhile, return and then things seem to become clear. Or at least, that seems to work in my case. With your electrical background you are much further ahead than the average person attempting to troubleshoot a high-efficiency furnace. I agree about starting fresh from the beginning. Check line voltage and grounds into the furnace. Check line voltage up to the transformer and 24V out of the transformer. Check across R and C terminals at the control board for 24V. If you do not have the 24V between the transformer and R and C terminals there is no need to go any further until that issue is figured out. I have seen water from the a/c coil condensate above the control board come down and get on the 12-pin plug. All control board manufacturers specify to replace the board if it gets wet. I have also a couple of cases where one of the the wires in the plug is not pushed in as far as the others and good contact is not made. I would suggest you really puish hard on the 12-pin connector to make sure it is fully seated and wiggle it around while testing for 24V between R and C.

At least a few labels as to what section a viewer is looking at would help.
Can you imagine the difficult time persons trying to help others on this forum have? It really helps when posters include some nice clear photos of the unit they are working on. Then persons trying to assist can label the photos or make better suggestions as to what they might try. It is the next best thing to being there. I recently had a person who had a contractor remove his thermostat without labeling the wires. The wires changed colors three times. Once he made a video of the wires at the condenser, the thermostat and the air handler it helped to quickly figure it out.

Your help is greatly appreciated and I feel guilty about taking up so much of your time.
No need to feel guilty. I enjoy helping others figure out their issues. This type of work is like being a detective; figuring out the unknown. I like figuring out why something doesn't work and making it work. Sometimes simple; sometimes a challenge. Of course, trying to diagnose a system sight unseen from hundreds or thousands of miles away is pretty difficult and we can only guess at times.
 
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Old 09-26-14, 02:28 PM
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I printed this last posting of yours and will follow it also. Now I am curious as what the actual problem is going to turn out to be. I am hoping it is just probably something I missed since this is the first time I have worked on a hi efficiency furnace. It is in a basement and the photos I did take were not turning out that well. Just about everything I did had to do with electricity. I started with RC Aircraft in the 50s and we had to build our own radios, they were crude but they worked, this was before the transistor was invented, and of course before ICs. Then I wired Homes and worked in a fabricating plant and did some Crane Maintenance and electrical installations before working for engineering companies. I spent 5 years in Houston, worked for Brown and Root for a while, and Dow chemical, so I know the furnaces and AC systems down there are in attics instead of basements. It must be like working in a furnace in those attics when people want their Air conditioners fixed, I can only imagine. I went into a few attics up here in mid day in the summer and that was enough for me. I am retired now, I still fly RC and now I like designing and drawing new different original designs. Radio control has really evolved now and now Drones are the rage now for some. Some of the kids today are pretty smart and I know they would tackle fixing one of these furnaces. It is a completely differently country than what I was born into and not always for the better. I still have friends in Texas that I keep in touch with. I also find it fun to help others at times when I can. I better end this now, I will get after that furnace tomorrow. (I learned to talk like that in Texas. By the way, I am near Pittsburgh PA., the furnace is in Pittsburgh.)
 
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Old 09-26-14, 03:11 PM
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I also am also very curious as to what the problem turns out to be. When I studied the wiring diagram it appears to me that there are two separate low voltage safety control circuits. The first starts at the transformer and goes through the rollout switches and then back to the R terminal on the control board. The second starts at the W terminal and goes through the two manual auxiliary limit switches, the high limit switch through the ID blower pressure switch and if that pressure switch is closed voltage travels to the front cover pressure switch. If that pressure switch is closed voltage is sent to the first stage terminal on the gas valve to start the flow of gas. To me, that would indicate if either (or both) of the two rollout switches are tripped 24V would not be sent to R from the transformer. If that is the case, re-setting the rollout switches should send 24V to the R terminal.

Based on your extensive extensive electrical and engineering background, is that the way you interpret that schematic?

Of course, if one or both of the the rollout switches did trip the cause would need to be investigated and corrected. Flame rollout usually indicates a problem with combustion or venting, possibly a restriction in the vent pipe, or something improper with the draft inducer. I would definetly check the vent pipe again to make sure it is completely open. Hopefully the installer put the correct pitch when he installed it and there are no sags to collect water. Even a leaf can cause problems.
 

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Old 09-28-14, 02:50 PM
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Your comment about roll out switches is making me think. I checked everything I could think of and could not get it to work. Reading your other posts as a check list, I saw a comment about taking one of the wires off of the inducer "pressure" switch, (which I now see as a "vacuum switch" being more accurate.) so I tried that again and remembered that I had tried that before and nothing happened this time either. Back to the Rollout switch, which I admit to not understanding what they mean by "rollout" and I only check this out by checking for continuity between RO IN and RO Out and there was continuity there. The White Rodgers, typical wiring drawing only shows a single switch and it is shown N.C. and the Goodman schematic has them looking like they could be N.O. That bothered me a bit but I figured they were really N.C. after looking at how the "pressure" switches were drawn, but I will remember your question. I was starting to go around in circles again with this. I did go outside and check the 3" PVC pipes again, they have down facing elbows, so there is not much chance for water to get in them. I also fished them with a thinner polyethylene tubing and they seem to be clear. After reading down through White Rodgers check list to see if I had checked whatever I could from their list, and about the LED supposedly to be on solid when the control board was working correctly, is when I called the original serviceman. He didn't recognize my cell phone number so he answered and I told him what I was trying to do, I didn't give him a hard time or anything about him avoiding this problem, so it really went pretty well. I explained what I was doing trying to diagnose the problem and get if fixed. He told me he had run into the exact same thing and the only way he could get that one fixed was to install a new control board and a new transformer. He agreed to help, since this board lasted only about 2 weeks. He is going to order another control board and transformer using the Model number and serial number I got right off the furnace again for him. Then we can go pick them up and I will install them. We are going to clean this furnace up before installing the new board. It is dirty enough to need a cleaning.

Now when I get this bad board out of this furnace, I want to investigate it further, after hopefully the new board and transformer solves the problem. One thing that still bothers me is that the ID "pressure" switch tests open, like the schematic shows, only after you remove one of the wires from it. With both wires on it tests closed. I am going to see if I can trace that when that board is on my work bench?? I did test both switches with my ohmmeter connected to them with one wire removed from each and by putting a vacuum on each tube the switches seem to work nice without too much effort. I keep thinking it might be a contact on one of those relays??, If its the IC causing the problem that's something else, but they do have ways to even change an IC, IF you could get one?

With the power off, which I also checked for H and N polarity just in case like I read on White Rogers list, I checked all of the limit switches and they seemed OK. There was no corrosion that would have made me suspicious of any of them. By this time I was running out of time and patience, so I called the previous serviceman, talked it over with him, he admitted to not being exactly sure what was wrong with the other one he fixed with the same basic problem. I also think he probably was glad to help to clear his conscience a bit on this one. This has been an experience. I sure appreciate your time and help and if I can come up with an answer some how? I will be sure to talk to you about it. One more thing, he said he found a burnt spot on the rear of the board, so he asked if I had checked that?, I did look at the rear of the board and it was nice and clean with NO burnt spot. A lot depend on these control board with their rather small components, miniature relays etc., but the original lasted close to ten years!
 
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Old 09-28-14, 05:04 PM
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Out of curiosity: Did you ever get 24V between pins 3 and 6 on the 12-pin connector? Did you ever get a 24V reading across R and C?

I saw a comment about taking one of the wires off of the inducer "pressure" switch, (which I now see as a "vacuum switch" being more accurate.)
The schematic for the unit you are working on shows ID Blower Pressure Switch. It is an air-proving switch or, as it is sometimes called, the draft-proving switch. It ensures there is airflow from the intake out through the vent termination.

If the control board "sees" the ID blower pressure switch closed it will not let the ID blower start up. The ID blower motor start up should be the first thing to happen after the control board checks to see if all of the safety devices are closed.

Back to the Rollout switch, which I admit to not understanding what they mean by "rollout" and I only check this out by checking for continuity between RO IN and RO Out and there was continuity there.
The rollout switch (also called a spillage switch) detects flames coming out the front of the burner opening (vestibule). Did you press the reset buttons on top of the switches?

The White Rodgers, typical wiring drawing only shows a single switch and it is shown N.C. and the Goodman schematic has them looking like they could be N.O.
Again, a person must go by the unit-specific schematic. All rollout switches I have ever seen are are N.C. They open when there is an over-temperature condition in the burner area. Some common causes are low gas pressure, low combustion air, plugged burner orifices, plugged heat exchanger. I see the ones on the Goodman unit-specific schematic as N.C.

I did go outside and check the 3" PVC pipes again, they have down facing elbows, so there is not much chance for water to get in them.
The water in the pipe would not be from the outside. It would be from condensation from exhaust gases. Proper installation of the vent pipe requires a pitch of 1/4" per foot towards the furnace. If the pipe is not supported properly it can sag and cause the condensate to pool inside the pipe at the sag effectively blocking exhaust gas.

He told me he had run into the exact same thing and the only way he could get that one fixed was to install a new control board and a new transformer. He agreed to help, since this board lasted only about 2 weeks. He is going to order another control board and transformer using the Model number and serial number I got right off the furnace again for him. Then we can go pick them up and I will install them. We are going to clean this furnace up before installing the new board. It is dirty enough to need a cleaning.
Why would the transformer be bad if you tested and got 24V out of the low voltage side and was able to start the a/c condenser by wiring the two a/c condenser control wires to it? I hope the board will be replaced under warranty.

One more thing, he said he found a burnt spot on the rear of the board, so he asked if I had checked that?, I did look at the rear of the board and it was nice and clean with NO burnt spot.
When I have found a bad control board it has always had a burnt area on the backside of the board. Not to say that it will always be evident. I have found bad grounds on control boards that others had installed.

I called the previous serviceman, talked it over with him, he admitted to not being exactly sure what was wrong with the other one he fixed with the same basic problem.
This guy (based on your description of events) doesn't give me a warm "fuzzy" feeling. He sounds more like a "parts changer". High efficiency furnaces are much more complex than the furnaces of old and not every "bubba" can troubleshoot and maintain them. The intake combustion air, the vent, the gas pressure and etc. all have to be within certain parameters to operate properly. Then the 95 percent units have two heat exchangers. The excuse about not wanting to return because of the dogs is extremely suspect. Doesn't he provide a warranty on his parts and labor? Two weeks and the unit he worked on already failed? He should at least come back out and check his work and verify proper operation of the control board and entire system. If he is a licensed HVAC technician he should be able to get the replacement board under warranty. If you install the replacement board, the warranty probably won't be in effect. The warranty is normally 12 months but only extends to a licensed contractor or hvac technician.

I certainly hope a new board will solve the issues with the furnace. If you don't get a solid red LED after resetting power to the board the troubleshooting guide states to replace it. Please keep us posted.
 

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Old 09-30-14, 10:03 AM
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You have valid points and questions. I think I remember having voltage across pins 3 and 12 and also across R and C and it still bugs me that I couldn't get the Condenser to start off of the control board terminals. I used your comments on printouts as a check list and checked point off, but now I see why I should have written comments on the EXACT findings instead. The fact that I had to resort to holding the red and white control wires of the condenser to FINALLY get it to run, still bugs me, because you well know that doesn't make sense at all. On top of that I agree why doesn't this prove the 24 volt transformer is still good, and that is one of the reasons I went directly to the transformer. I do remember when I tried to start the condenser from the 24 volts on the terminals, with my voltmeter also connected, the voltage just dropped to 0 when I connected the red and white wires. I have experience with electronics, but I don't consider myself an expert with these Hi efficiency furnaces, but again, I will remember this experience and I think I will stay curious enough to fill in the blanks eventually on what I don't know. I won't be trying to become HVAC licensed, I am too old to add another career to my Resume, I am 75 now, and I have other things going on.

(I did install Envirosafe refrigerant, instead of R12, in my Ranger pick up, it works better, has less load on the engine, and only took two 6 ounce cans instead of the 36 ounces required for R12. It stopped working with R12 in it and had VERY little R12 left in it, just hooking up the old gauges got rid of that. The instructions said pulling a vacuum is not really necessary, so I didn't and got great results from an AC system that hadn't worked in 2 years. The truck is actually 28 years old. You don't need a license with these substitute refrigerants. I do LIKE to do things myself and have told others about this stuff to help them.)

The first question I asked this serviceman, being careful not to irk him, was about the warranty on the board, and what he said was after you remove the plastic film, the warranty is gone. I didn't think that was how it is, but myself and my brother at this point just want to get the furnace working and that is why I didn't even question his advice to install a new transformer. After I got him to agree into putting into a will call order for these parts, which is going to be a better price that I could get off the net, I agreed to doing this. I gave him the Model Number and Serial number and he read them back to me. now he has yet to call and said the order is ready to be picked up. I will probably need to bug this guy, because I never let customers hanging with electrical work, but I saw it done by others.

You are probably correct, he might not be licensed, but he must have an account with a supplier. Whether or not they require a copy of a license to even open an account, I don't know.

Your comments here have me wondering about what I said about the roll out switches again. On the manufacture's drawing which is to be considered the valid certified drawing, of course as you say, the switches, if you look close, they look open, I agree. Myself I was more particular in drawing anything to make sure it was clearly understood, so I had doubts on this. Again I didn't write down my findings, but I think I remember there being continuity between pins 5 and 3, the orange and red wires from the manual reset rollout switches, and I don't know if this furnace has one or two, I need to check the BTU size of the unit, I suppose, and I I need to check the wiring to recheck the location of these switches. I think I did that before, but that I don't remember. I just might go there again and might need to go look up the serviceman in person. (If he doesn't get on the ball here, I might be tempted to bring the Dogs with me. If anyone starts giving my brother or even me, a hard time, they pick up on it and can make that someone nervous? lol.) The board still looks new and I "still" would not be surprised IF it turns out to be something I didn't uncover even with your help. Whatever, I sure will keep you informed and anyone else following this thread, its becoming a mystery saga, and maybe because of my inexperience?
 
  #26  
Old 09-30-14, 11:19 AM
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As far as the rollout switches there should be two on the furnace you are working on. If you still want to troubleshoot it a little further before installing the new board, I would put a jumper between RO1 and RO2 on the 12-pin connector. These are 5 and 11 going into the plug and should be an orange and red wire. Sometimes it is a little difficult to get the jumper wire in with the existing the wire. I carry a couple of small diameter sewing needles to use when necessary. This jumper will fool the control board into thinking the rollout circuit is closed (as it should be during pre-start up and during operation). Then pull off the wire from one of the terminals of the ID blower switch. Then jump R and W at the terminal board. As soon as the ID blower starts up quickly plug the wire back onto the ID blower terminal. If the ID blower motor starts up and goes through the ignition sequence that would tell you the control board is not the problem and would point to another component or issue.

As mentioned earlier, the ID blower pressure switch has to be OPEN or the ID blower motor will not start. That is because if it was closed voltage would be sent to the next pressure switch and then to the gas valve. The pressure switch is a safety that prevents the gas valve from opening if there is something wrong such as a blocked air intake or vent pipe. Once the pressure switch is closed it sends voltage up to the other pressure switch to see if there is a problem with the condensate draining. If you refer to the wiring diagram you can see what I mean.

Testing the rollout switches is a simple process. With power off, remove the two wires and test for continuity from terminal to terminal. With power on you should test for 24V to ground on either side.

Another method you can do to test out the safety switches such as the limit switch is to bypass them one at a time. A method I use to join the two wires going into the switch is to use an automotive blade fuse (like the one on the board). Of course, these safety controls should only be bypassed for testing purposes.

You can test for continuity between pins 1 and 10 to see if the two auxiliary and main limit switches are closed.

During your last visit did you get a change to check the port on the ID blower to make sure there was no crud in it? That crud in the ID blower port can cause the pressure switch to not operate properly. Also, were you able to identify the two auxiliary limit switches on the sides of the blower housing and push the reset buttons?

As far as the warranty on the board White-Rogers warrants the board for a year to an hvac technician/contractor. What the guy said about once the control board is removed from the wrapper the warranty goes away doesn't pass the common sense or "smell" test. When you go to pick up the new board at will call I would ask the counter guy if there is a warranty on the old board. It doesn't hurt to ask. Of course, they will more than likely ask for a receipt or which account number was used to purchase the board.

In the attached photo I labelled the two rollout limit controls, two pressure switches and the primary limit control. The diagram shows the location of the two auxiliary limit controls (manual reset).
 
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Last edited by firedawgsatx; 09-30-14 at 01:35 PM. Reason: Added photo
  #27  
Old 10-06-14, 07:04 AM
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The furnace is working fine, in large part, because of your help. Thanks again. This thread ended up having a lot of information that you posted, and this will help others I am sure.

I read through this last post of yours what the roll out switches were at the time, but I had checked them and they were fine. I had guessed the limit switch WAS a limit switch and it checked correctly. I didn't know there were limit switches on the blower housing, The blower motor and capacitor had been changed the year before also. I saw all of the wires going back to the blower, and I did check the system at the 12 pin connector by following the terminal block drawing from White Rodgers and the schematic from Goodman, while you were taking me through it all. I understand it a lot better now. All of my continuity reading were checking out according to the schematic at the 12 pin connector.

The "no start" problem was at the two pressure switches with the black hoses connected to them, so everyone knows what we are talking about here. Originally you told me these switches need to be open or the furnace WON"T start. I found out right at the beginning that, with all of the wires connected to everything, the ID pressure switch was showing closed. After you told me to "put a vacuum" on the hoses to see if the switches operated, then the name "pressure switch" wasn't confusing the issue.

With the wires on these switches, the ID pressure switch was showing closed as I said and there was also continuity through the Front Cover pressure switch. When I had the wires OFF these two switches with my ohmmeter connected to them, they seemed to work fine with the vacuum I put on them. By the way those black rubber hoses don't taste very good. With the wires back on these switches, the actual resistance reading were around 200 ohms across the OPEN terminals of the Front Cover switch, and only around 5 ohms across the terminals of the ID pressure switch. I got these same readings across the wires, WITH THE WIRES REMOVED FROM THE SWITCHES, and I had found this early on, but I don't think I made this clear enough in the beginning, and Of course you weren't there, and you couldn't see what I was doing, AND I didn't realize these PRESSURE switches actually operate by VACCUUM.

After I checked this, with the power off of course, with the new control and transformer installed, after I checked twice to make sure I had all of the wires correctly connected to the new board. I checked the "pressure" switched again and got NO continuity resistance readings, so I turned the power on and the furnace started normally, and it has continued to operate well. We also checked to see if the AC would come on and it is working also.

One thing I hadn't seen before with the instructions that came with the control board was 24VAC HIGH side and 24VAC LOW side for the description of the 24 volt transformer. I thought I remembered which wire went where on the 24 volt transformer, but to check it, I saw on the schematic that the OR (orange) wire was across from the black wire on the 120 VAC input of the transformer so I figured the OR wire must be the HIGH side of the 24VAC power that ends up on TH of the 12 pin connector.

I think I got that right, but I didn't understand why this is important. I suppose it means something to the electronics of the control board, the processer and the other ICs. (Everything has a "processer" now.)

My brother picked up the control board and transformer, he didn't even think to question the supplier about the warranty, he just wanted the furnace to work.

I have the old control board, and old transformer. I am curious to check it further to see what I can find, if I can find anything?, as long as tracing the circuit doesn't take me to the processer, maybe I can find something? The original control board had some surface mounted components, resistors etc., and at least these newer ones seem to be better with no SM components. The 3rd control board is in there now and the 3rd is exactly the same as the #2 that went bad. The Model number and Serial number were given to the supplier to order both times, so there is little chance the wrong control board might have been installed as the #2 board, and the dead #2 board still looks new, (the components are larger and should be more reliable?).

This has been an experience. I couldn't have done it without your help and especially with your giving me the link to the PDFs of the schematics. When I talked to the serviceman, he told me he had replaced another control board in a furnace that created the same problem this one had and he didn't understand what was going on, so he replaced the board and transformer, and why we decided to do the same, to make sure the furnace got fixed.

I will tell the serviceman this story as a courtesy to him because he did help somewhat by ordering a new board. (Maybe he had a credibility problem with the supplier on that earlier job, by bringing bad board(s), back for the warranty??)


This has been a learning experience I will remember, and now there won't be as much of a mystery to that 92% Trane I have in my own basement. (I am behind in cleaning it also.)

Thanks again.
 

Last edited by old electrician; 10-06-14 at 07:26 AM. Reason: minor punctuation and added 1 word
  #28  
Old 10-06-14, 08:07 AM
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I am really glad to hear you got the system back up and running and thanks for the update. I'm glad I was able to help in a small way.

One thing I hadn't seen before with the instructions that came with the control board was 24VAC HIGH side and 24VAC LOW side for the description of the 24 volt transformer. I thought I remembered which wire went where on the 24 volt transformer, but to check it, I saw on the schematic that the OR (orange) wire was across from the black wire on the 120 VAC input of the transformer so I figured the OR wire must be the HIGH side of the 24VAC power that ends up on TH of the 12 pin connector.

I think I got that right, but I didn't understand why this is important. I suppose it means something to the electronics of the control board, the processer and the other ICs. (Everything has a "processer" now.)
These transformers have a "hot" side that supplies 24V to the thermostat to power the other terminals to send voltage back to the control board depending on the mode selected (heat, cool or fan) and a common side which connects to all relays to complete the circuit. You are correct that the orange wire is the "hot" or high side.

As far as the pressure switches, those were some strange readings you were getting. As you know, there should be no continuity if the switch is open and continuity if the switch is closed. These readings should be taken with the wires off.

Anyway, the bottom line is the system is back up and running. The positive thing is that you added another dimension to your vast technical experience.
 
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Old 10-08-14, 11:24 AM
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At one point, I did explain that I had tested the switches with the wires off and they were open as they should be. It is the bad control board that has the continuity problem. I have the control board here and visually it LOOKS fine. I haven't tried to do any checking of it yet but I will, IF for no more than my curiosity. Right now I just finished another project, remote mounting of an ignition module that Ford mounted on the distributor, It let me down in two rush hour traffic jams lately, so that project came before any more investigating of the control board, and before I got into an accident. This was the first time I got into a complicated servicing problem with help coming over the Internet, it was interesting to say the least, and very much appreciated.
Firedawg, that is an interesting user name I will also remember, thanks again.
 
 

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