Gas heating - Gas Valve or Circuit Board?

omgsobe

Hello all,


UPDATE 2/13/2021- The Heat furnace is still working since the replacement of the circuit board.

I've been reading the forums here and had two folks with the same issue as me, but they did not answer back with the result. What a bummer. I could tell that you guys were disappointed. I assure you I won't be that way.

Pretty much new to the heat furnace world and right now, I feel like I'm close to being a technician (sarcasm). So about 2 weeks ago when I woke up one morning, the fan was blowing constantly with no heat.
I thought it was the thermostat. I did some research and was told it could be the igniter. I checked the furnace and the igniter lit up bright orange. I scratched that out. But I replaced the thermostat anyways because I wanted a programmable one.

Then later I researched and saw it could be the flame sensor. I took out the flame sensor, and it didn't really look that bad, but I've already touched the flame sensor with my hands. However, I went ahead and ordered me a flame sensor, and I put it in without touching the metal piece. I turned the main switch on and gas valve switch on. The furnace went through the process and there was no flame. I turned off the switches again. I tried again and wiggled the wires a bit. I unplugged the wires from the flame sensor and sticked it back in. I looked at the circuit board and wiggled the wires just a tad bit. Then I turned the main switch on and turned the gas valve switch on, and it went through the process. I saw the flame!

Well I thought that solved it, but the back of my mind I thought there might be something else like the wiring or the circuit board and left the attic.

So it has been working for about 2 weeks up until now when I woke up to go work, it was cold. So I know it couldn't be the flame sensor. There was loud thundering and pouring rain that night, but I'm not sure if the elements could cause the heat to stop functioning.

I googled and youtubed for 5 straight hours that I felt like I knew so much about the heating system. I debated if it could be the circuit board or the gas valve at this point. I heard that the gas valve could go bad or the circuit board as well. I wanted to test this out. So when I got home, I started messing with the furnace again. Here's the part that I am not good at - testing the gas valve with the multimeter. I googled how to test the gas valve, but it's quite different. Of course, I set the black to COM and the red to VAC at 750 and while trying to test the gas valve, the red wires has a protective shield over the end of the terminal so I can't really test it. I was thinking about buying a tester that clamps over the wires? (Is that what I need to do?) I am very nervous about testing things near gas. But I am willing to try if you provide me the proper procedure.

So I stopped the testing and I started messing with the wires. I unplugged the red and dark blue wires from the gas valve and plugged back in. (By the way, I left the gas switch on but turned off the main switch.) So I turned the main switch on and still didn't work. So I looked at the circuit board and unplugged the wires and plugged back in. I held the cables and you know, just wiggle or seeing what it can do. I turned the switch back on and I saw the flame. So this time I wanted to see consistently, so I turned off the main switch and left the gas valve switch on. I waited couple of seconds and turned it back on. I see the flame again! I am positive it could be the circuit board at this moment. So 30 minutes later when the house got warm, it tried to start back up. Then it went to safety mode with the fan blowing. I went back up to the attic and did not see the flame. I turned the switch off and left the gas valve switch on. I wiggle jiggle the wires. I flicked my fingers lightly to the circuit board capacitors what not. I made sure the wires are plugged in securely on the circuit board. I also unplugged the wires from the gas valve and put it back in securely. It worked. I see flames! The house is heated up. It started back up after it got cold. So it's working as of now 7:36 pm eastern time.

But still, I am not 100% sure it could be the circuit board. It still could be a bad gas valve? I am hoping that it could be the circuit board because I can just buy and replace it. However, I am going to replace the board anyways. I have a d341122p01 50A55-571 circuit board and my furnace is a Trane xb80.

I can get pictures if needed. I only got pictures of the board and not the gas valve but I can go back up to the attic if I need to. But it's a pain getting up there.

What do you guys think? Board or Gas Valve? Or will I need to buy a volt tester that will test the wires via clamp style.

Thank you for taking the time to read this long story.

Abracadabra

What's the flash code seen on the board after failure to ignite?

BobC

I've worked in electronics all my life and I can tell you flaky circuit boards are a real problem. You could well have a cracked solder joint. Try poking around with a toothpick or something similar to see if you get it to change state with the power on.

Also try moving each wire in that molex connector it could be a bad crimp or a cracked joint under one of the pine on the boards connector.

While your doing this use one hand and keep the other in your pocket so you don't zap yourself.

Bob

omgsobe

Thank you for your response Abracadabra:

The flash code after failure to ignite were two flashes. Here is the picture of the diagnostic codes:


Thank you for your response Bob. I sure hope so. I checked Amazon for the circuit board, and the buyer said he had the issue that I was having. When he replaced the board, it worked fine. I'll try your tip IF I get no heat again.

I still don't want to rule out the bad gas valve.

Thank you.

Abracadabra

Can you feel if the gas valve solenoid clicks when attempting ignition? Test for power at the gas valve.

ratio

A flash code of two is in line with the gas valve not opening. You can unplug the wires from the gas valve & stick the test probes into the terminals on the end of the wires, then turn the furnace back on & watch for around 24-27 volts to appear a few seconds after the ignitor starts to glow. It's low voltage & protected by a fuse, so there isn't a lot of opportunity to get hurt or damage anything. If the ignitor goes out without power appearing that's a pretty good indication that the board is bad. Another test of the gas valve is to switch your meter to the ohms or resistance range & put it on the terminals of the gas valve (control board unplugged). You should show low resistance, but not zero & not open circuit or infinity.

omgsobe

Abracadabra: I don't feel it, but hear clicks (maybe like 2) after the igniter does it thing.

Ratio: I did what you told me. I turned off the switch and turned off the gas valve switch. I took the two wires out, red and dark blue. I took the test probes and connected the red to the red wire and the black to the dark blue wire. When I turned on the main switch, nothing powered on. I saw the circuit board blinking slowly with constance. Then I plugged the wires back into the gas valve and turned the main switch back on. No power at all to the furnace. The inducer even did not come on. The only power I saw was the red blinking light from the circuit board. I really got worried thinking I shorten something out. Few minutes later, it started back up and I saw flame.

So I started the process again. Turned off the main switch and gas valve. Got the probe to the ends of the two wires. I turned the main switch and after the igniter does its thing, I got a reading between 25, 26, 27. I was kind of upset. So I waited for it to cycle again and it gave me the same reading 25, 26, 27.

So we are assuming it is now the gas valve? What would be the next thing to do? Hire a technician to replace it?

I didn't do the ohm resistance reading because I was uncomfortable. Not sure what you meant by control board unplugged? Do you mean unplug every wires from the control board?

I am still glad that the flame still come on after the test because i was afraid it wouldn't.

Here is a picture of the gas valve.




Thank you

omgsobe

So, it's been working properly and it's 9:35pm eastern time. It rested and now just started back up to warm the house to reach its temperature.

What if overnight, it suddenly stops working? Would that be because the gas valve didn't open up "anymore" after 3 tries then going to safety mode? Or would that be because the "supposedly" bad circuit board didn't generate a 24-27 volt to the gas valve after 3 tries then going to safety mode?

Should I replace the circuit board anyways?

ratio

What the flash code is telling us is that, for some reason, the furnace didn't prove that it had a flame after three tries to light, or that the flames went away & it had to relight three times. It also appears to be an intermittent problem, which makes diagnosis that much harder. At least occasionally the unit will light, more or less correctly. 25, 26, 27 is about right for the power to open the gas valve. A slow steady flash means that the thermostat isn't telling the furnace to fire. It seems that it's fairly unreliable—not a long wait for it to fail. What I would do next is turn the thermostat up a few degrees so that it wants to heat. Then go to the furnace, switch it off & back on to make it restart. Listen carefully to the gas valve. You're looking for two things. First, you want to hear (or feel with your hand) a >CLICK< a few seconds after the ignitor gets hot. Immediately after the click, you should hear gas hissing in the burners, which should light nearly immediately. If the burner lights properly, switch it off for a few seconds and try it again. We're looking for what exactly isn't happening. No click means that either the board isn't powering the valve or the valve is failing electrically. A click but no gas hissing means that the valve is failing mechanically. A click and gas hissing but no ignition means that we aren't lighting properly.

omgsobe

So that's what abracadabra meant by feeling. I was afraid to touch the gas valve (for some reason, or get too close to it) when it's starting up. I'll definitely try that later and will let you guys know.

I went ahead and ordered a new circuit board even if this gas valve supposedly having intermittent issues.

Side thoughts: Could it also be for some reason messing with the wires fully generated a 24v to the gas valve "for now"? Where before, it would work and suddenly just stops producing flame? Then again, could be the mechanical issue with the gas valve not opening at that moment, but then again, why all of a sudden I mess with wires it started to work? Ahhhhhh.

I'll keep you guys updated with new findings even and if/when I put in the new board that will arrive next week unfortunately.

Thank you

Jamie Hall

Have to admit -- and what I know about gas valves and ignitors and all is close to zip -- that when I have something which works sometimes, and messing with wires makes it work (or not), the first place I start looking is at all the wires and connectors and plugs. Which often go bad... someone said there is a Molex connector in there somewhere? Those things are tricky. They're great when they're good. They don't stay good...

Abracadabra

There will be a click from the relay on the board. There will be something more like a tap/click from the gas valve. They will be simultaneous, so putting a finger on the gas valve will help narrow down whether the valve is reacting to signal from the board.

ratio

And yes, messing with the wires can sometimes "fix" it, more or less temporarily. That points more towards a wiring issue, does not rule out a board issue, and makes a mechanical gas valve issue less likely. If it's been running more reliably since you fiddled with the wires/connectors, I'd unplug & plug everything in the gas valve harness a few times, & look carefully at the connections for signs of corrosion or mechanical failure.

omgsobe

Update:

At 12:00 PM noon eastern time, I noticed that the "heat" was blowing cold air. I went up to the attic and saw no flame. So I turned off the main switch and tested the two wires taking out of the gas valve. The first reading I got was 2,3. The second reading, I got was 19,20 somewhere around there (I know it was under 24-27 for sure). The third reading I got 24,25. I tested again and got the reading 20, 24. Seems like it was inconsistent.

So next step, I plugged the two wires back into the gas valve and turned the switch on. I did not get any flames. I placed my hand on the gas valve and the black tube that goes into it. I feel like there's gas roaming in there as there was vibration (or maybe it could be the inducer blowing to it), but I did hear hissing sound during the the igniter process, and I did not hear a click in the gas valve which of course no flame. I turned off the switch, messed with the wires again and went to the circuit board and flicked one of the capacitors and jiggled the wires. I turned on the main switch, touched the gas valve and black tube. I felt the gas roaming (maybe inducer blowing) and heard the hissing sound during the igniter process, and I heard a CLICK in the gas valve, and then I got flame!

What do you all think? Bad board or bad wires? I'm learning towards that. But won't be sure until I receive the new board. Will keep you updated.

Thank you all for all the input thus far.

Thank you

j a_2

How is the incoming gas pressure static and dynamic? Did you test the pressure switches? Is the condensate line clear? Disconnect it and blow thru it....If ugly brown condensate comes out you may find your issue....Jump or the thermostat at the unit to save your energy.....High or low pressure gas area?

j a_2

Jump the t stat to save energy going up and down the stairs is what I meant....You did check the vent and intake....for obstructions......Feel free to disconnect one at a time and run unit....Just be careful on the exhaust....Once you get it up and running see if you can get your hands on a combustion analyzer...Couple of supply houses in Boston used to loan them out to plumbers....Because we always sent ours in when the calibration date was up.....

ratio

Erratic voltage could be caused by a loose connection/bad board, but could also be caused by poor connection of the probes—it's sometimes hard to get them to stay in a connector like that. Follow the wires from the gas valve back to the big white plug (left side in your 1st pic) and see if you can jam the probes into the same hole that the wires goes in to, one in each, with the meter set to a voltage scale like you have been using. We're looking for 24-27 volts when the gas valve should be opening like before, but with a more reliable connection.

omgsobe

Don't think I can jam it in there. I tried before, and it just won't unfortunately. The picture sure does show roomy for the probe. Maybe I'll have at it if the heat breaks again. Also the probe was brand new and never opened for 2 years. But of course, new stuff doesn't necessarily mean that it's flawless.

Well Heat has still been working since I fiddled with the wires and capacitors/fuse last week.
The new board came in yesterday. Not sure if I want to replace it yet. Maybe I'll wait until it quits working again and then replace.

ratio

If it settled down after you manipulated the wires, that points to (but does not confirm) a loose/corroded connection. Leave it until it you notice it's not working again.

omgsobe

Ok Update:

This morning, my heater failed. I got the vent blowing cold air and went up to the attic and no flame. I turned off the switch and turned back on. Still no flame. I didn't test the volt unfortunately. I unplugged the big white "grouping of connector" and plugged it back in. Then it started working again. I turned off the switch and turned it back on, and flames came back on again. I am starting to think if it's the something with the board and don't think it's the "grouping of connector." I went ahead and switched out the board since I am off work today.

Very straight forward on replacing the old board. Took a picture and video and unplugged the wires and plugged back in with the new board. Went to my breaker and turned it on - then turned on the switch in the attic and the gas valve, and it immediately work just fine. I switched off and switched on to make sure it can still function and it did.

I checked the back of the old board and one area in the middle looks brown, like it's the end of its life.. maybe.

However, I'm not going to rule out "the grouping of connector" JUST YET. I'll give it more time - but as far as I know, it's flaming.

Thank you for the help and tips again!

Sobe

Tim McElwain

I see you used a universal replacement board.

rick in Alaska

I have had a lot of problems with that molex connector ( grouping of wires). If it goes down again, I would look carefully at each one of the pins and see if any look "different" than the others. Sometimes one of the pins will get opened up too far and lose contact.
I also had one of those boards with the molex connector that drove me crazy on nuisance lockouts until I got a very bright light on the back of the circuit board and found a cracked solder joint on one of the pins. New board and problem gone.
Rick

omgsobe

Tim: Is the universal board a bad thing? I'm curious now. That was the only thing I was able to find and after checking the reviews on Amazon that people were able to use the "universal model" from the original one.

Rick: Thanks for the tip. I'll check the molex connector next time. But, I hope it doesn't fail on me again. It's very time consuming and frustrating.

ratio

Congratulations omgsobe, you can now add "HVAC service technician" to you CV!

Tim McElwain

Universal board is okay you just have to make sure it cross referenced with the original control. Ebay Amazon and other outlets is not always a safe way to find the correct controls.

Sal Santamaura

Tim McElwain said:

Universal board is okay you just have to make sure it cross referenced with the original control. Ebay Amazon and other outlets is not always a safe way to find the correct controls.

Even cross referencing might not be sufficient. After confirming our malfunctioning furnace's gas valve and other sensors were OK a few years ago, I purchased the "correct" non-OEM replacement board via amazon.com. Installation was straightfoward, and everything "worked." However, I noticed that the delay between flame and main blower start was longer than expected. Concerned about damaging the HX, I contacted the new board's manufacturer's tech support line. After some explanation, they put me through to the engineer who designed that board.

Bottom line: the manufacturer re-worked firmware, overnighted me a new board incorporating the correct delay and paid for pickup / return of both my scrap OEM board as well as the one purchased through amazon.com. A typical consumer (I'm an electrical engineer) would probably not have been sensitive to the main blower activation time change and ruined their HX. At this point, unless one is very technically inclined, I'd recommend going with an OEM board rather than saving a few dollars on the generic.

Or call a qualified contractor.

LauriBuell

Hi....i also think that you have a cracked solder joint. Try poking around with a toothpick or something similar to see if you get it to change state with the power on.Try moving each wire in that molex connector it could be a bad crimp or a cracked joint under one of the pine on the boards connector.

pcb assembly process

maba

> @omgsobe said:
> Tim: Is the universal board a bad thing? I'm curious now. That was the only thing I was able to find and after checking the reviews on Amazon that people were able to use the "universal model" from the original one.
>
> Rick: Thanks for the tip. I'll check the molex connector next time. But, I hope it doesn't fail on me again. It's very time consuming and frustrating.

Please advise that if your furnace is still working fine. I have the same furnace XB80 Trane and the exact same problem.

HVACNUT

Universal furnace circuit boards are usually fine as long as it covers your specific model.
Check the dip switches if any.
And some universal boards give you a wiring harness or two to replace or adapt to what's there now.
Take pics and label before you remove any wires.

ratio

HVACNUT said:

Take pics and label before you remove any wires.

QFT!!!1!

Don't forget this step. It'll save you a lot of heartache later.

Mill1978

Hello I'm new to HVAC but have the exact issues.... I've replaced two valve a board and transformer.....still on go.

Tim McElwain

Throwing parts at a problem is never a good idea. It actually pays to hire a professional and be done with it. However knowing how folks are some pictures and numbers of the original controls would be very helpful. By the way do not throw away the controls you removed as you may need to put them back.

DZoro

@Mill1978 Start a new thread. With some details of what you are experiencing, and things you have done. Pictures are of help to us also.
D

Glennc

I have a very similar problem with my old Lennox 80UHG 4/5-100a-3 furnace. Gas valve was not kicking on during the ignition cycle. I measured the voltage coming into the gas valve and I was only getting 12v and is supposed to be getting 24v. I jiggled the wires at the harness and it fired up! Well, it was working fine and cycling on and off as normal for about 8 hours, then it stopped working. Jiggled the wires again and took a measurement from the board to the gas valve. This time I only got 6 - 8v. Wow.
I removed the wire harness, brushed it off, inspected it and all looked good, notching loose or scorched. Then I looked at the circuit board from behind and couldn't see any cracked solder joints but there is a bit of brown discoloration on the circuits between the resisters next to the harness and the big controller chip? Maybe like it got hot? What do you think bad board?
Not wanting to spend $200 to find out.
Thanks for your help and sharing this info! Really appreciate it.

Glennc

Here are some pics of my board. The yellow and blue wires go to the gas valve. Can you see the brown discoloration in the middle of the board?

SuperTech

I'm pretty sure you can replace that sure light board with any universal Honeywell or White Rodgers. I'd actually rather use the Honeywell S9200U, Lennox boards seem to be junk.

Leonard

No experience with your board, but I've repair lot of stuff. In general browning of circuit boards don't always mean a bad component, sometimes stuff on them normally run hot and boards discolor.

omgsobe

maba said:

> @omgsobe said:

> Tim: Is the universal board a bad thing? I'm curious now. That was the only thing I was able to find and after checking the reviews on Amazon that people were able to use the "universal model" from the original one.

>

> Rick: Thanks for the tip. I'll check the molex connector next time. But, I hope it doesn't fail on me again. It's very time consuming and frustrating.


Please advise that if your furnace is still working fine. I have the same furnace XB80 Trane and the exact same problem.

Leonard,

I am the OP. Yes it's still working

ssankaran80

I've been having the same issue.  Got the gas valve and pressure switch replaced but the hest doesn't come on consistently. Technician suggested to replace the chip board. The hvac is a goodman one and is hardly 1 winter old.

HomerJSmith

Blue and red wires on the plug going to the gas valve? Pull the board and check the solder joints on the back of the plug and look for a solder break. If you find one you can resolder the joint with rosin core solder. Clean the old solder off with solder wick.

I had the same thing happen on a Lennox furnace and the tech before me replaced the gas valve which wasn't the problem. The problem was a solder break on the blue wire on the back receptical that blue wire went to the gas valve.
For informational purposes only.

109A_5

I realize this an old post. However for informational purposes only (even with the poor picture quality) the solder joints circled in Red to the Molex connector look a bit suspicious.