Furnace failing


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Old 02-21-08, 06:02 AM
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Unhappy Furnace failing

Hi everyone. We have a Gibson GL1RA 108C-16B natural gas furnace (forced air, hot surface igniter, pre-lubricated/sealed air blower motor bearings) in our house and it seems to be failing. The diagnostic lights on the circuit board are indicating an "Ignition Failure (Check Ground)" fault condition. However, I've checked the ground connection and it seems to be fine. No changes have been made to any of the electrical circuits in the house, so I highly doubt it's an electrical ground issue. The furnace is about 3 years old. We actually have two of them, the one going bad is the bigger one that's down in the basement. The smaller one hasn't had any problems so far. All the fans on the furnace are operating correctly and the igniter coil is fine. However, after the coil warms up and the gas valve clicks open there is a grinding noise and the burners fail to turn on 80% of the time. When they do turn on, they either only do so for a couple of seconds and then immediately shut off, or they turn on but the gas flow sounds very turbulent. Is this the gas valve failing or is something clogged in the manifold? Any help would be appreciated. Thanks!

Here is a video (23.3MB, MPG, 67 seconds long) of the furnace attempting and failing to ignite burners. The valve gas click and noise can be heard toward the end of the video. The camera is rotated so the top of the furnace is the left side in the video. You might have to right click on the link and "Save As" if it's not opening in your browser:
http://www.ornus.org/images/furnace_...8/MOV00027.MPG


A couple of pictures of the inside of the furnace can be found here:
http://www.ornus.org/images/furnace_failing_02212008/

Here is the manual for the furnace:
http://www.discountheatandair.com/pr...e%20gibson.pdf

Update:
Just checked the voltage across the gas valve terminals. I'm getting 15VAC instead of 24VAC. I'm assuming it's the ignition control module that's failing. Am I right?
 

Last edited by sarotara; 02-21-08 at 08:41 AM. Reason: More information added.
  #2  
Old 02-21-08, 10:28 AM
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I replaced the control board in the furnace, but it's still not working.
 
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Old 02-21-08, 11:57 AM
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Are you getting 24 volts at the gas valve shortly after the igniter starts glowing?
 
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Old 02-21-08, 12:21 PM
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Here is what happens with regard to voltage across the gas valve terminals:

1) Furnace switched on
2) Fans turn on for about 30 seconds - 0.5VAC
3) Audible click, igniter element starts glowing for several seconds - 0.5VAC
4) Another click + grinding noise for several seconds - 15VAC
5) Yet another click, grinding noise goes away - 0.5VAC
6) About 1-2 seconds later the igniter element goes off - 0.5VAC

#2 through #6 happen several times in a row
 
  #5  
Old 02-21-08, 12:29 PM
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Is the circuit board getting 24V? It might need a new transformer.
 
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Old 02-21-08, 12:53 PM
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If the transformer checks out ok, then check the wiring between the gas valve and the board. Many units have limit switches in series with the gas valve. A bad or loose connection is another possibility, as well as a bad limit switch (high resistance). You should also check for 24 volts where the gas valve wiring connects to the board.
 
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Old 02-21-08, 02:55 PM
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Thumbs up most definitely impressed

And very impressed I must emphasize...
in looking at the video and pics.

Well...the grinding noise is indeed due to the improper (low) voltage.

I'll put my 2 cents tonight (if still needed) once done with a few house chores.
 
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Old 02-21-08, 05:43 PM
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O.K., here we go...please perform the following tests
(1) look at the pic below. Pls disconnect the two control transformer's secondary wires...one is Black with white stripes, the other is White with black stripes
(2) on these wires, please take a voltage reading (hook one tip of the voltmeter to the white wire terminal, the other to the black). "Live Power" pls, I want to know what the voltage is in the secondary. I expect it to read 24V

IF it reads 24V, move to step-3. If it reads 15V, pls check the voltage on the primary side of the transformer. The pic below shows you where is the transformer (component #9)

The primary side wires should be a white and a black...You may check with the voltmeter by touching on terminals XFMR and NEUTRAL on the board (see red arrows on pic below)



The reading should be 120V. IF indeed the primary reads 120V, a 15V reading in the secondary indicates a bad transformer...replace. If both, Primary and secondary readings are normal (120V-Pri, 24V-Sec), move to step-3

(3)REMOVE THERMOSTAT from the wall. Leave on the wall ONLY the subbase.
(4) put a jumper between terminals W and R at the subbase. If the furnace starts and all is normal, you have a bad thermostat. Replace.


More tests later...For now, pls perform the tests mentioned above. By performing them we will either find the source of trouble, or, will eliminate the transformer and thermostat as possible culprits for this malfunction.
 
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Old 02-21-08, 06:06 PM
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Man, that's impressive, pflor
So were the sarotara's

Posting pics and videos can help a LOT
 
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Old 02-21-08, 09:09 PM
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Hi everyone. I just came back home and the furnace was running (temperature in the house was 64 deg. F, I set it to 68 deg. F, it's about 20 deg. F outside). I checked the voltage across the gas valve terminals again (I'm checking at the yellow and brown wires coming out of the 9-pin connector on the control board) and it read around 19.5VAC. Since I bought a new transformer I decided to install. After installing the transformer the voltage across the gas valve terminals still reads 19.5VAC.

pflor, I will do the tests that you suggested and will let you know the results in just a bit.
 
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Old 02-21-08, 10:18 PM
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pflor's test results

Thanks for all the replies and all the help. I really appreciate it.

I checked the voltages as suggested:
- transformer primary side reading - 122.9VAC
- transformer secondary side reading - 26.6VAC

As for the thermostat check. I removed the front cover of the thermostat, removed the batteries and waited about 30 seconds. I then placed a jumper wire between the W and R terminals. The furnace seemed to start normally. That would mean a bad thermostat I take it? How does placing a jumper wire across the W and R terminals show that the thermostat is bad?
 
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Old 02-22-08, 01:23 AM
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To put it simple, the job of the thermostat is to, kind'a, put automatically a jumper between R and W whenever the house starts getting cold, and to remove the jumper once the house is nice and warm. So, what you did manually (jump R & W) is done automatically by the t-stat.

The t-stat is then a switch. But a smart one. All it is expected to do is to allow power to go from terminal R in the transformer to terminal W in the board, by the closing of an internal set of contacts, but WITHOUT causing a voltage drop.

It appears though, that in your case, for whatever reason, a voltage drop of about 11-to-12V is taking place as power goes from the transformer (Terminal-R), thru the thermostat, on its way to the board (Terminal-W). Enough of a drop to be causing the mayhem you reported.
WHY? I don't know without knowing the MFR & M/N and seeing pics of its installation: a close-up of the subbase (thermostat removed), AND a second close-up with the t-stat in place.

If this thermostat was recently installed and trouble started right after it was installed, then it either came defective or it has been improperly wired/installed.

I'll be looking forward for your feedback in this matter.
 
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Old 02-22-08, 02:06 AM
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Furnace Help

You know you have over 24v coming out of your transformer, you also know you have less than 24v going to your gas valve voltage drops due to resistance I would unplug and plug every wire from your gas valve to your control board then try lighting furnace again. If the problem persists then take voltage readings across any safeties between the gas valve and the board if the voltage is not dropping across the safeties then there is increased resistance in your board if this furnace is less than 5 years old they will give you a new board
 
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Old 02-22-08, 02:30 AM
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one last test

Before replacing that thermostat, one more test in order, just to make sure that it is the thermostat and not the board (or safeties) the source of the trouble. Mike n's point is well taken.

With the thermostat removed (only the subbase on the wall), put back again that jumper between R and W. The furnace shall fire. Go to the furnace and take one last reading at the terminals of the gas valve. If now you're reading 24V, then definitely the thermostat is the source of the troubles. Else, follow up on Mike n's recommendation.
 
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Old 02-22-08, 09:06 PM
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All right, I will check this out sometime tomorrow and let everyone know what happened. Thanks for all the suggestions and help so far. I really appreciate it.
 
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Old 02-23-08, 10:28 AM
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I took the top cover off the thermostat, took out the batteries, put a jumper between R and W, and checked the voltage across the gas valve terminals. It's still reading 15.5VAC. I also tried bypassing the thermostat completely by taking out the batteries, putting a jumper across the R and W terminals on the control board, and taking a reading across the gas valve terminals. Still reading 15.5VAC. In either situation the furnace still refused to turn on. So I guess it's not the thermostat. I'm assuming it's not the control board because I replaced it. I double checked all the connections too and everything seems to be connected correctly. I don't understand why it would have read 19VAC yesterday and it's reading 15.5VAC today. The furnace is not working again (as of this morning). Any other ideas as to what this could be? Thanks in advance!
 
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Old 02-23-08, 11:02 AM
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Something is shorted there, and from your report, it sure is not the thermostat.

Do you have one of these there: (a) A humidifier?, (b) An elctronic air cleaner?
If so, please unplug their terminals at the board.

Then, at the board, look for the thermostat terminals (R, W, G, Y and C) and disconnect all five thermostat wires from the board.

After having done the above, take a new reading of Pri & Sec voltages at the transformer. I hope you'll read 120V (Prim) and 24V (Sec).

At the board, at the thermostat terminal strip on the board, put a jumper between R & W. Once the furnace fires-up, please take a new reading of transformer voltages (both, Pri & Sec)...if the unit fires and the voltages at the transformer are normal, one of these may be happening:
1- bad thermostat cable from thermostat to the unit
2- problem with humidifier (if you have one installed)
3- problem with Electronic Air Cleaner (if you have one)

You also say that you replaced the board. A missing ground would be a source of trouble too...When dis you replace the board? they are polarity sensitive, you can't switch L1 for N.

Are we sure we have the right board?
 
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Old 02-23-08, 12:10 PM
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I've seen boards act funny when the low voltage side of the transformer is plugged on the board backwards as well.

This thread is getting interesting, love the pictures and video!

Michael
 
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Old 02-23-08, 12:31 PM
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Phew! I sure am glad you find the thread interesting...as for me, I'm starting to run short of ideas/recommendations and I imagine poor sarotara is probably frustrated.

Only thing I haven't recommended yet is that sarotara uses a sledge hammer to get this fixed once and for all.
(just kidding...leave the hammer in the toolbox)
 
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Old 02-23-08, 12:35 PM
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I will recheck all the connections once again, measure the voltages, and post the results in a bit. However, we do not have a humidifier or an electronic air cleaner. The board was replaced last two days ago. Heading down to the basement now to check everything.
 
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Old 02-23-08, 01:43 PM
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All right, I rechecked all the connections. It's definitely not the thermostat since when I disconnect the thermostat wires and placed a jumper between the R and W connections on the control board, the gas valve voltage terminal reading was still 15.5VAC. I rechecked the voltages at the transformer. Anywhere from 26VAC to 28VAC. I checked the transformer connections against the electrical schematics that were provided as a part of the installation manual and everything seems to be connected correctly. I took a bunch more pictures of the unit. The ignition board is still flashing the "Ignition Failure (Check Ground)" code.

You can find a bunch more pictures of the furnace unit and a short video of the control board flashing the Ignition Failure fault code right here:
http://www.ornus.org/images/furnace_failing_02232008/

Any other ideas/recommendations would be highly appreciated. I might just take pflor's recommendation and "fix" the furnace with a sledge hammer.
 
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Old 02-23-08, 02:01 PM
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And yet some more tests...I'm not giving up on you!

Disconnect both wires connected to the gas valve. With the meter set for continuity (ohms), place one lead of your meter on a metal surface (that is not painted) and the other on one of the two gas valve terminals...you should have an open circuit reading (infinity)...do the same by now switching the lead from the one valve terminal to the other.
Any resistance reading, other than infinity, would tell me that you have a grounded gas valve coil. Replace valve if so.

There is a 9-wire harness that connects to the board just underneath terminal W. Unplug and plug back again (make sure the connection is firm and goes all the way).
Terminal #9 in this wire harness (top left corner of it) is the ground connection. Make sure is firm on both ends, at the screw where it hooks up to ground, and at the board itself.

From terminals #8 (mid-left) and #3 (top right) in this wire harness you should be able to see two blue wires (one from #3, the other from #8). These connect to the rollout(s) and limit(s). Put a jumper between these two blue wires (at the safeties ends, not a the board...which would be too difficult to do). This would bypass the limit(s) and rollout(s). If they are the source of the trouble, with the jumper they would be no more. Disconnect the two gas valve wires and connect to the terminals of your meter set for voltage readouts, place a jumper at R&W on the board (call for heat)...within a minute or so I expect a readout of 24V on the meter. Reconnect the gas valve wires and call for heat again from the board; wait for the unit to fire and read transformer voltages, as well as the voltage at the gas valve. Report.

Again from the wire harness at the board, terminal #2 (mid-right) has a brown wire, terminal #4 (bottom-center) has a yellow wire...these two wires go to the gas valve. Make sure the ends of these wires at both, the board and the gas valve are secure. Make sure the jumper at the end of the blue wires stays in place. Call for heat by jumping between R and W at the board...take a reading of voltage at terminals 2 and 4 AT THE WIRE HARNESS (not at the gas valve). You should read 24V. If the reading is 15V, by taking the reading at the board, I believe is safe to assume that the board is not good.

How can we be sure that the board you have been given is the right one for your unit? who purchased it? where? Can you provide the board's M/N? this should be checked with the mfr., to be sure is the right one.
 
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Old 02-23-08, 02:53 PM
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pflor, you are a genius! Bypassing the rollout/limit switches did the trick. Getting 27VAC through the gas valve wires now. Reconnecting the gas valve wires to the valve causes the furnace to fire up with no problems. Time to replace them the switches!

To everyone (and especially pflor) that posted and helped with this problem... thank you! I really appreciate the help and the time everyone put into this. Thanks again!
 
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Old 02-23-08, 05:46 PM
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By the way, I played around with bypassing the various safeties, and it turns out that it was the limit switch that's bad. I will have to wait until Monday to replace it, since the store that sells the switches is closed on Sundays. I'm assuming it's ok to set the thermostat to about 62 degrees F or so until Monday, or will I burn the house down if I bypass the limit switch temporarily?
 
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Old 02-23-08, 05:49 PM
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As I sometimes teasingly tell my youth soccer players when they get a moment of inspiration and score: Lucky shot!...
Glad to read things worked out for you.
 
 

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