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York Diamond 90 Gas Furnace - blowing cold air now, was blowing hot air this am

York Diamond 90 Gas Furnace - blowing cold air now, was blowing hot air this am

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  #1  
Old 10-12-09, 02:07 PM
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York Diamond 90 Gas Furnace - blowing cold air now, was blowing hot air this am

Hi all,

My problem is similar to another thread with a similar title. I started a new thread on the advice of SeattlePioneer so it would be less confusing.

I have a York Diamond 90 furnace blowing cold air. From what can tell (see detailed description below), the burners are not getting lit, although they clearly were just a few hours ago. And I apologize in advance if I get any terminology wrong; please correct me if so.

Background: I have only one gas appliance in the house: the furnace. So I bought this house in May, and just had the gas turned on last week (didn't need furnace before now!). I cannot check whether gas is still entering the house, aside from taking a look at the meter, which looks fine and is in the "on" position. There was obviously incoming gas this am, so I don't know what could have changed there.

What is happening: This is about the third day I have used the furnace. It was blowing hot air this morning and then began blowing cold air midday. I went to the basement to watch it in action. The igniter begins to glow, glows steadily for a few seconds, then the glow goes dark slowly. It is then dark for about 25 seconds. Then the cycle repeats itself. It will continue to do this for as long as I have the thermostat set to a higher temperature than is the current temp in the house. The blower is going, as is the fan. However, I do not see any flames anywhere inside the burner box.

What I have checked and tried:
Vent pipes: There is no vent pipe connected to the intake; it just sucks inside air in from the basement. It is clear and I can put my hand over it and feel it sucking in air. The outgoing vent pipe looks fine; no obstructions. One post in this thread said that the air intake might need to be more "restrictive." I tried restricting the flow with some thin fabric held over the intake. When I did that, the igniter turned off. So then I tried putting my hand just slightly over the intake. Again, the igniter seemed offended and turned off.

Condensate pump: I don't think this is it. I installed a new condensate pump last week (the old one was falling apart), but I don't think the furnace has been operating long enough to generate enough condensate to trigger the thing.

Error light: There is no error light at all. I watched it for several boring minutes.

Air filter: Brand new and clean.

Burner cover: I finally took off the burner cover and tried to see if the burners would ignite then. They didn't. The igniter just continued its usual 30-second on-off cycle.

So.... From the other posts I have read here, it seems like there is something wrong with the igniter or with the gas supply entering the burner box. I would really like to try to fix this myself; I am fairly handy and find myself with more time than money these days (pretty common, I suppose!).

What would be the best first step? Call the gas company about the possibility of poor gas flow? Replace the ignitor? Move the ignitor slightly? Do something with the burners (clean them or something)? Something else?

Sorry for how long this post is and thanks in advance for your replies! I will be sure to get back instantly with answers to any questions.
 
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  #2  
Old 10-12-09, 02:46 PM
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A furnace typically has a "sequence of operation," a series of things that must happen in order for it to produce heat.

That the hot surface ignitor lights tells us how far through that sequence the furnace is getting and what should happen next.

Typically the HSI would heat up for 20-30 seconds and then the electric gas valve would turn the main burner gas on, the gas burners would light and stay lit, and after another minute or so the fan would turn on to circulate warm air.

When you say that the HSI turns on for "a few" seconds ---- just how many seconds is that?

Can you hear a "click" from the electric gas valve suggesting that the valve is opening? Can you hear or smell gas from the burners or furnace?


If the main burners fail to light, the ignition module turns the gas off after 3-5 seconds or so, and the ignition process begins again as you describe.

Check to see if the shutoff valve for the furnace is on and that the gas control on the gas valve is turned to the "on" position. You want to be sure that the gas is on all the way to the furnace and the electric gas valve.
 
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Old 10-12-09, 03:09 PM
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Okay. When I turn the furnace on:
-The blower starts up 2 seconds after I flip the switch.
-The HSI starts to glow 5 seconds after I flip the switch. It reaches its brightest glow 10 seconds after it first began to glow. It maintains that brightness for about 2 seconds. Then it turns off, which takes about 2-3 seconds for it to become completely dark.
-Right as the HSI becomes completely dark, the fan that pushes air to the registers comes on and stays on.
-The blower stays on for a total of 35 seconds (it continues being on even after the HSI has shut off). After 35 seconds, it shuts off for one second. After one second, it starts again, and then the HSI begins to glow 3 seconds later. This cycle continues indefnitely. Meanwhile, the fan that pushes air to the registers stays on continuously.

The gas control on the gas valve is in the "on" position. And the shutoff is on as well (it is parallel with the gas pipe).

I cannot hear any "clicks." I placed my left hand on the gas pipe that comes into the valve and my right hand on the gas pipe from the valve to the burners and could not "feel" any clicks either.
 
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Old 10-12-09, 04:31 PM
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It seems that the gas valve may not be turning on the gas for the HSI to light.

If you have an AC voltmeter, check to see if you have 24 VAC across the gas valve after the HSI heats up.

The HSI should warm up, then you should get 24 VAC across the gas valve which ought to turn the gas on to the burners. After 3-5 seconds or so, the 24 VAC should turn off since the burners haven't lit.

Either:

1) you still don't have gas to the gas valve

2) your ignition control isn't turning the gas valve on by supplying 24 VAC to it to turn it on

3) or the gas valve is off, defective or burned out
 
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Old 10-12-09, 05:13 PM
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Thanks for all your help.

I think 1 is unlikely, because all the gas shutoffs are in the "on" position. Unless there is some way the gas company can shut off your gas remotely and for no reason? I haven't even received a bill yet.

So that leaves 2 and 3. I will buy an AC voltmeter tomorrow and check the gas valve. If I AM getting 24 VAC, then it's 3 (the valve is defective or burnt out). If I'm NOT getting 24 VAC, then it's 2 (there is something wrong with the ignition control).

Glad I have an electric blanket. Will reply tomorrow with the results of the voltmeter. Thanks again.
 
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Old 10-12-09, 05:21 PM
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The gas is probably on, but you never know. Lots of strange stuff can happen.


There should be a union in the gas piping between the furnace shutoff valve and the electric gas valve. If it were me I'd turn off the gas at the shutoff valve and then open the union. Turn on the shutoff valve again briefly to verify that you have gas pressure.
 
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Old 10-12-09, 05:25 PM
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Originally Posted by PDXer View Post
So that leaves 2 and 3. I will buy an AC voltmeter tomorrow and check the gas valve. If I AM getting 24 VAC, then it's 3 (the valve is defective or burnt out). If I'm NOT getting 24 VAC, then it's 2 (there is something wrong with the ignition control).

.


Yes.


You are getting an idea of how to repair furnaces. You need to be able to identify how far along in the furnace's sequence og operation you are getting before the furnace will go no further.

Then you need to identify the possible reasons why it wont make the next step.

And then test the various alternatives to identify which one is causing the problem and eliminating the other possibilities.
 
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Old 10-13-09, 09:46 AM
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Well, we can totally rule out 1, because the gas is definitely on.

I borrowed my brother-in-law's multimeter. On the gas control valve I placed the black probe on the terminal with the black wire and the red probe on the terminal with the yellow wire. I don't have down-to-the-second time measurements because both hands were holding the probes and I couldn't write everything down. Here are my 6 iterations of turning on the furnace:

-1st time: When I turned the furnace on with the probes on the gas control valve, it went through about the first 15-20 seconds or so. When the HSI got to its brightest point, there was a popping/clicking sound and the burners came on! The VAC was 23.2. I was so shocked (hardy har) that I took the probes off the terminals. About 5 seconds later, the burners went out. Then I watched for another couple minutes, and the furnace went through the cycle that I described yesterday, with no ignition and no clicking.

-2nd time: I did the same thing but kept the probes on the terminals. I kept them on there for about 2 minutes, during which time the VAC ranged continuously from 23.2 to 22.5. The burners stayed on the entire time.

-3rd time: I turned the furnace on WITHOUT the probes on the terminals, there was a "click" about 20 seconds in, and the burners ignited by themselves, as described in the first iteration above. So the furnace turned on by itself, with no help from the probes.

But it turned itself off after a few minutes of heat, and when it started up again about 20 seconds later, it was blowing cold air. I watched the furnace cycle through its failed ignition cycle a couple of times, then placed the multimeter probes on the terminals. The burners lit as described in iteration #1, and I let them run for about 10 seconds before taking the probes off. They stayed on.

But it turned itself off after a few minutes of heat, and when it started up again about 20 seconds later, it was blowing cold air.

4th, 5th, 6th times: Probes on the terminals, but no ignition and no VAC. It just cycles through its failed ignition cycle.

So: The gas control valve clicked on by itself ONCE, in the middle of all these tries. Three times, it needed the multimeter probes on the terminals to click on. But after that, the gas control valve wouldn't click on even with the multimeter probes on the terminals, and there was 0 VAC.

Also, another detail I just now noticed while I was staring at the gas control valve (sorry I didn't see it earlier): where the gas pipes enter and leave the gas control valve, and where the piping is joined together on the run, there is white teflon tape, not pipe dope or yellow teflon tape.
 
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Old 10-13-09, 10:53 AM
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Also, should I be getting some type of error code? Is it possible that there is something wrong with the LED unit and that we are thereby missing crucial information? It just seems odd to me that the furnace can be clearly malfunctioning in this manner and there is no error code.
 
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Old 10-13-09, 11:35 AM
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Gas valve still not sending gas to burners, but I did open the door at the bottom of the furnace and trace the wires from the gas valve down to where they enter the White-Rodgers furnace control box. I tried to push them further into the plastic connector and push the connector further into the box (to ensure solid connections).

When I tested the VAC at the gas valve, I got 0.9 VAC for about one second (at the point at which the HSI is brightest and when the gas valve previously was getting 23.2 and clicking).
 
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Old 10-13-09, 03:46 PM
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need to make a decision

Hey guys, I'm just hanging out here. I have been searching this forum and others all day, but I can't seem to find anyone else who has had the exact same problem.

Is my description of what's going wrong just horribly convoluted? Are there any more details that I can provide you?

Are there any clues you can give me based on what I've provided? Really, anything would be helpful, even just a guess or two.

I'm sure you guys are all really busy and I know your work here is unpaid. I really appreciate the help that you've given me so far. But at some point soon, I need to make a decision. Either I continue trying to fix this thing myself, or I suck it up and call a repairman.
 
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Old 10-13-09, 05:46 PM
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I just got back form working on a Heil furnace, where I had the inducer in pieces on the floor.

Anyway - With all your testing you are doing, test the 24VAC voltage into and out of the pressure switch when it runs, to see if the outflow current is being shut off. If that shuts off, so does the gas valve and ignition. The inducer may keep running though. When pressure switch or internal pressure of the furnace is not quite up to snuff for any reason, it can be so on the bubble, that one minute it will work, the next minute it won't, or, even run for a while and up and quit. With some pressure switches, you are actually able to watch the plunger that pushes on the switch, to see what it is doing. Often you can see it going in and out a little bit.
 
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Old 10-13-09, 10:24 PM
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The voltage into the pressure switch is only 6.6 VAC. The VAC out is the same. What does that mean?

I can't see any parts of the pressure switch moving, unfortunately.

And the HSI is working all of the time. It's just the gas valve that works intermittently; it receives around 24 VAC some of the time (when it "clicks" and ignites the burners) and about 0.6-0.9 VAC at other times (when it doesn't click and there is no ignition, although the HSI is getting hot.)
 
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Old 10-14-09, 08:12 AM
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As I read more about furnaces and try to get a grasp of their sequence of operations, I don't think it's the pressure switch.

Correct me if I'm missing any crucial steps:
1. Call for heat
2. Inducer fan starts
3. Pressure switch closes
4. Circuit board recognizes the pressure switch closure and verifies that limit and rollout switches are closed also
5. Circuit board energizes the hot surface ignitor
6. Circuit board energizes the gas control valve
7. Burners light and are recognized by the flame sensor
8. Main blower starts and hot air comes out of the registers.

With my furnace, everything appears to be happening except for Step 6. Step 6 (the burners lighting) happens every so often, but not consistently or predictably. So the furnace ALWAYS blows air, the HSI ALWAYS ignites, etc., but the air is only hot when Step 6 has taken place. What I need to do is figure out why Step 6 is not happening; that is, why the gas valve is not opening.

The clues I have are that sometimes the gas valve receives around 23VAC and "clicks" and other times it receives around 0.6-1.1VAC and doesn't do anything. Another thing is that the pressure switch is only getting 6VAC to 9VAC at each of its terminals. But it is still closing. Is that normal?

Could it be that there is a malfunction at the main circuit board that is sending about 23VAC to the gas valve every once in a while and around 0.6-1.1VAC most of the time? And should the the pressure switch be getting 24VAC?
 
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Old 10-14-09, 08:20 AM
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Are you testing so that say the red probe is on the one pressure switch spade and the other black probe is put to a good metal ground on the furnace? And that you either are contacting a known good ground good, or you are trying to scrape into the metal to enure good ground? Or to make sure ther eis not soem groudnign issue, yiou can put the black probe directly to the transformer common terminal. (Nothing bad will happen if you pick the wrong wire to test. The worst that wil happen is you will not get a reading at all if you are on the wrong wire, since you would be in series with it.) Also, if you are putting the red probe to say a brass looking terminal that is part of a 90-degree spade connection on the pressure switch, do not go by that. I believe they may have clear-coated that exposed part, and sometimes getting a good contact on that is hard. In that case, slide out the female spade connector some, and probe right to the part the female spade slips onto. Also, for the incoming wire of the two, you can also remove it from the switch itself, and test right into the female spade itself -at least to see if you are getting 6.6 or about 24.

IF you still get that low reading - if -then go back to the transformer and test between the 2 24 volt wires.
 
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Old 10-14-09, 08:34 AM
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Yes, I am testing so that the red probe is on the one pressure switch spade and the other black probe is put to a good metal ground on the furnace. I'm not sure how to evaluate a good ground, but I am definitely touching the other probe firmly to bare metal, and the bare metal is part of the furnace that sits directly on my basement floor.

And this time around, my readings are about 16-18VAC at the pressure switch.

I will go test at the transformer also.

Do you have any advice regarding the gas control valve?

Thanks for your help.
 
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Old 10-14-09, 08:45 AM
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Let's resolve the voltage issue first. Most furnaces are somewhere between about 24 and 26.5 that I have worked on and had reason to test.
 
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Old 10-14-09, 09:23 AM
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I traced the wires out of the pressure switch. One (the blue one) goes directly to the furnace control panel. I tested that one at the point where it enters the furnace control panel and it was giving me the same reading (about 16-18VAC).

THEN I traced the white wire out of the pressure switch. It goes to the high limit control, where it joins with another white wire at the terminal. I tested the voltage at that terminal, and I got 24VAC! Then the furnace started up correctly! Now it appears to be working just fine. The voltage at the pressure switch is now 24VAC.

But now I am just more confused than before. Why did I all of a sudden start getting 24VAC?

I am going to turn the furnace off and see if it will start up again by itself.
 
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Old 10-14-09, 09:34 AM
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I just turned it on twice.

The first time, it went through one cycle without the gas valve releasing the gas. During that time, I got 24-25 VAC at both the pressure switch terminals and at the high limit control. When I put my probe to the yellow wire going into the gas control valve (during the second attempt to ignite), it clicked, I got 24 VAC, and the burners ignited.

I then turned the furnace off. When I turned it back on, it started up correctly the first time. However, now it seems to have shut off again. I am going to go test the voltages again, and I will test at the transformer.

This may be a really dumb question, but what could make the voltages swing around like this?
 
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Old 10-14-09, 09:43 AM
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Well, now it's working just fine. So I don't really see what testing I can do; it's hard to test what's wrong when it isn't going wrong at that particular moment.

I think maybe the next time it breaks, I will just call a repairman. Or just go down to the basement and poke the multimeter probes all over the place, because that seems to be what makes it start working again. Sigh. Causation or correlation, who knows.
 
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Old 10-14-09, 04:18 PM
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It broke again. Called the repair guy. Five minutes and $85 later... the control module is shot. $500 to replace it.

It's a 20-year old York furnace. New Carriers are about $3000 after various rebates. Repair or replace; anyone got an opinion?

And again, thank you all for all your help and suggestions.
 
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Old 10-14-09, 04:39 PM
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Call around or look online as that is a ridiculous price, I'd say. You can DIY a control module, if you buy one. The last actual control board (not encased ignition control modules, as I have had to put a number of those in)I had to put in that had various relays even on the board, with many wires that plugged in, only cost me $125 a few years back. Even let's say if it cost $200................
 
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Old 10-14-09, 05:20 PM
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I'm getting confused about terminology. Here is what I need to replace: White-Rodgers #50A50-241. My furnace manual calls it the "Furnace Control." But when I product search it, it's called various things, including "WHITE RODGERS UNIVERSAL SILICON CARBIDE INTEGRATED HOT SURFACE IGNITION CONTROL."

So I'm not sure whether it's a control board or an encased ignition control module. It does say "not field repairable" on it and appears to be pretty encased.

Soooooooo. Whatever it is, I can get it for under $100. However, I am concerned that my abilities may not be up to snuff for this particular DIY. I am decent at wiring and plumbing, having put a second bathroom in from scratch in my house and done a down-to-the studs kitchen remodel. Is this thing is pretty "plug and play"? Can I just turn off the power, unhook all the wires the old one (being careful to mark where they all go!) and then hook all the wires up to the new one and fire it up, and be all good? Or are there calibrations or other mysterious activities I will need to undertake?

I am intrigued by the idea of doing this myself, but I don't want to get in over my head...

Advice?
 
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Old 10-14-09, 05:22 PM
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Similar problem

I have a York heater that is around 9 years old. When i switched on, I can hear the blower fan running. It continues to run. There are no other changes. I did not hear any clicks. I dont see the ignitor heating up. The gas burner never lit. I do have gas flowing inside the house as my gas fireplace is working and the gas runs to both furnace and the fireplace from the same junction. So, I am certain the gas is flowing. However, I dont smell any gas. Please help.

OP- Sorry, I did not mean to interrupt your thread. However, I thought this is the best place to find a answer for my problem as it seems to be similar to yours.


----Update-----
For some reason, my heater decided to work. I have no idea why it did not work for couple days. Anyway, thanks.
 

Last edited by augustinm; 10-14-09 at 06:15 PM.
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Old 10-14-09, 06:03 PM
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Originally Posted by PDXer View Post
I'm getting confused about terminology. Here is what I need to replace: White-Rodgers #50A50-241. My furnace manual calls it the "Furnace Control." But when I product search it, it's called various things, including "WHITE RODGERS UNIVERSAL SILICON CARBIDE INTEGRATED HOT SURFACE IGNITION CONTROL."

So I'm not sure whether it's a control board or an encased ignition control module. It does say "not field repairable" on it and appears to be pretty encased.

Soooooooo. Whatever it is, I can get it for under $100. However, I am concerned that my abilities may not be up to snuff for this particular DIY. I am decent at wiring and plumbing, having put a second bathroom in from scratch in my house and done a down-to-the studs kitchen remodel. Is this thing is pretty "plug and play"? Can I just turn off the power, unhook all the wires the old one (being careful to mark where they all go!) and then hook all the wires up to the new one and fire it up, and be all good? Or are there calibrations or other mysterious activities I will need to undertake?

I am intrigued by the idea of doing this myself, but I don't want to get in over my head...

Advice?
Sounds like you have an ignition control module, and you confirmed that by your description. However, I have to reread your thread to determine if I feel a failure with that could be causing your problem.

However, there are some control boards out there that perform more functions than your run of the mill ignition module. I can't recall the brand, but they are like side-by-side encased/connected modules.

Furnace guys make mistakes you know. Not all graduated phi beta cum laude (made that up......you know what I mean)It is easy for them to guess, replace a part off their truck and go, "hmmm,...... well, I guess we'll try this then." Why not, if you have all those parts on hand. For someone like me, I cannot afford to make mistakes. I don't have extra parts. I don't relish misdiagnosing control modules, boards or valves.

Replacing an ignition control module is as easy as it gets!!!

All you have to do is transfer your half-dozen or so wires from your old unit to the new one (if the module is an exact replacement, that is!). ...to the same terminals that are marked.

You just have to make sure that the letters or abbreviations are the same. Some manufacturers redesigned them, so they can work in several makes of furnaces - and that is what complicates things. But as long as you can read their instructions, you can do it. Some changed models will tell you that if your furnace has 'this' (whatever 'this' is), that you may have to use 'this' connection terminal and maybe remove a jumper wire or something. But if you have comprehension skills, you can do it!l I'm sure even furnace guys have to read some of them instructions and follow them.

Yesterday I had to change out a ventor fanblade kit. This came with step by step instructions, that I believe are meant for furnace men to read, not homeowners. So you read it and do what they say(even though I really did not need to, but did anyway).
 
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Old 10-15-09, 08:25 AM
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Thanks for being so encouraging. I ordered the part, so after it arrives in about one chilly week, I'll give it a go.

If it looks too daunting, I'll start calling around and see what the labor would be to have a pro install it.

Probably be talking to you again in seven days or so...
 
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Old 10-15-09, 05:05 PM
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Don't pull off any wires from the old control until you are certain where it goes on the new one. If need be(advised), take a pen and paper and write down what color wire goes to the same abbreviated labeled connection on the new one. Go by what the abbreviation says, not by where it is located, as they may have redesigned it!
 
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Old 10-26-09, 09:35 AM
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After replacing circuit panel, doing same thing but now with 4-flash error code

I'm back. I just successfully installed the new White-Rodgers circuit board/panel/ignition control module. Unfortunately, the furnace still won't work. It's behaving in the exact same way as before (see long detailed description earlier in the thread), with one minor difference: it now takes maybe 20 seconds longer to cycle through the failed ignition. From the documentation included with the new control panel, this is just because the new panel has different timings for the startup sequence than did the old panel.

BUT I am getting an error code now. So there's one positive thing. 4 flashes, which apparently means that a limit switch is open.

I was reading the other thread called "York Diamond 90 Gas Furnace - Blower runs - no heat with burner cover in place" where another person was getting the 4 flash code. The suggestions were:
-check air filter (mine is perfectly clean, and I am currently operating the thing with the bottom compartment open so I would assume the blower is getting all the air it could possibly need)
-make sure cold air returns are unblocked (mine are wide open)
-make sure the "A" air conditioner coil isn't dirty (frankly, I don't know if I even have air conditioning and I don't know what this is. If this could be my problem, could you tell me how to investigate it?)
-increase blower speed (I will happily do this if you can tell me how)
-check the low voltage wiring harness (mine appears to be fine, but I could disconnect and reconnect everything if you think it's a good idea)

I could also replace the limit switches or jumper around them, I suppose, if you think it would help.

Any advice? If you need more info, let me know.

Thanks in advance.
 
  #29  
Old 10-26-09, 12:02 PM
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"Percussive maintenance"

I think I've discovered why sometimes the gas valve opens and sometimes it doesn't.

Okay, so when I push hard on the left side of the the spade terminal where the two white wires join together and enter the primary limit switch, I can get the gas valve to open and the burners to ignite. But when I release the pressure, the gas valve closes and the burners shut down and I get my 4-flash error code again.
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Revision: Now I can get it to function just by giving it a little whack with a screwdriver. If it shuts off, I just give it another tap and it will usually start up at the next ignition cycle.
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So... should I just buy and install a new limit switch? I'm already down $96 for the new control panel (probably an unnecessary expense, although now at least I get error codes as opposed to getting nothing with the previous control panel), so throwing a little more money at this beast is fine with me.
 

Last edited by PDXer; 10-26-09 at 12:33 PM. Reason: new info
  #30  
Old 10-26-09, 01:55 PM
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<<So... should I just buy and install a new limit switch? I'm already down $96 for the new control panel (probably an unnecessary expense, although now at least I get error codes as opposed to getting nothing with the previous control panel), so throwing a little more money at this beast is fine with me.>>


I wouldn't bother, especially if you have a kid or a wife who can be trained to whack the limit switch when it starts to get cold. If you don't, then of course a new switch makes a lot of sense.



Seattle Pioneer
 
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Old 10-26-09, 04:03 PM
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PDXer,

I see your light is on and am wondering if you are pondering SP's response.
 
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Old 10-26-09, 06:10 PM
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Hi Ecman,

I have been pondering Seattlepioneers response... I priced out limit switches; I was under the impression that they were about $15, but this one (A Camstat FAL-3C-05TD-120-A) seems to only come along with the fan and costs $165! Does that make sense to you?

Also, the guy who I paid to come out here and tell me the control module was shot told me that this furnace is 20 years old. I have been operating under that impression. However, did they even make 92 AFUE furnaces 20 years ago? I found only one date on the thing and it says 1997. Any input? The model # is P3URD20N13001C, serial # EMGM460809.

Finally, I got the thing to run for about 20 minutes and it got the house all warm and toasty. But then I started to think that I smelled something burning. I got worried and went down and put my hand on the sheet metal that the limit switch is mounted to. It was so hot I couldn't keep my finger on it. Is that normal? Or was my limit switch actually doing its job of shutting down an overheating furnace and my whacking on it somehow broke it so that it is no longer performing its safety function?
 
  #33  
Old 10-26-09, 06:47 PM
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Originally Posted by PDXer View Post
Hi Ecman,

I have been pondering Seattlepioneers response... I priced out limit switches; I was under the impression that they were about $15, but this one (A Camstat FAL-3C-05TD-120-A) seems to only come along with the fan and costs $165! Does that make sense to you?

Also, the guy who I paid to come out here and tell me the control module was shot told me that this furnace is 20 years old. I have been operating under that impression. However, did they even make 92 AFUE furnaces 20 years ago? I found only one date on the thing and it says 1997. Any input? The model # is P3URD20N13001C, serial # EMGM460809.

Finally, I got the thing to run for about 20 minutes and it got the house all warm and toasty. But then I started to think that I smelled something burning. I got worried and went down and put my hand on the sheet metal that the limit switch is mounted to. It was so hot I couldn't keep my finger on it. Is that normal? Or was my limit switch actually doing its job of shutting down an overheating furnace and my whacking on it somehow broke it so that it is no longer performing its safety function?
Ever touch 140-200 degree metal? Well you just did, and it is hot. And that can be a normal range that includes operating temps, on up to the limit temp.

If you smell burning odor, go and see if you smell it coming out of a register, or if you mainly smell it only by the furnace.

If the limit switch is shot, which SP aluded to , that does not mean the furnace will 'run on' and cause the furnace to go into melt down. Instead that will kill the burner flame.

Where is that limit switch mounted? Off hand it makes no sense why the two are sold together as a package. We'd maybe have to see a picture. If this were true, sounds like they have a racket going. I have just replaced limit switches from 20 year vintage furnaces before, for cheap. But they are those simple thermal disc things on an arm(that goes through the sheetmetal above the burner) that is on a fiber material baseplate. Very simple.

OR -Now do you mean it comes actually with a fan? Or do you mean the limit switch also comes with the fan switch?...a limit/fan switch comb?
 
  #34  
Old 10-26-09, 07:30 PM
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Sorry; I was confused about the terminology with the limit switch. Apparently, it is what you said at the end: "Or do you mean the limit switch also comes with the fan switch?...a limit/fan switch comb?" It is not a combo of the FAN and the limit switch, but the fan SWITCH and the limit switch. They call it a "Fan/Limit Control," which confused me. "Fan Control/Limit Control" would be clearer for dunces like me.

Here is a link to one page showing the actual part: heatcoolparts.com/fanlimitcontrolpage.html. Scroll down to:
FAL3C-05TD-120A, 3", $109.60 (It was more like $160 on the other pages I saw; this is the cheapest I could find).

I got the impression it would be cheaper from another thread earlier this year where KMBORZAGE said: "In my previous post of 1/03/09 I express some of the same symptoms as others of you (Chilly-in-Chico). I took all of the good advice from others in this forum and learned more about my Diamond 90 system than I wanted. I eventually replaced both the flame sensor ($7) and the upper limit switch ($18), neither of which were probably responsible for my problem."

But I guess I'm stuck with shelling out another hundred bucks. As long as it works.... I'll let you know.
 
  #35  
Old 10-27-09, 10:58 AM
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Victory

Well, none of the camstat reps would sell me the damn limit switch because I'm a homeowner and they only wholesale. I finally had to go through an HVAC contractor who was really reluctant to sell me the thing ("I usually never sell limit switches to homeowners, but you sound like you know what you're doing") but finally did.

Put it in, and the furnace fired right up. Working like a dream.

Thank you all SO MUCH for all your help. My husband was getting a little tired of a cold house and me spending all my time in the basement tinkering. Feels good to finally have something to show for all this time spent.

I'll cheers you tonight when I have my victory beer(s). Beer 4U2
Thanks again,
Monika
 
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Old 10-27-09, 11:17 AM
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Great news! How much did they soak you for it?
 
  #37  
Old 10-27-09, 11:27 AM
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$125. I figure it's only a little bit more than I would have spent getting it online (especially with shipping). And it's nice to buy local.

So in the end, $85 for the guy to tell me it was the ignition control, $96 to buy the ignition control, and $125 for the limit switch. A little over 300 bucks; could be worse.
 
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