Valve and thermocouple good. Pilot will not stay lit

Tneily

I am at a total loss. Its getting colder and I can't get my pilot to stay let for anything. Pilot assembly is clean with a strong blue flame. The control valve is good. New thermocouple that's throwing out 28. Positioning looks good and no kinks. I don't understand what is going on. Any information shared would be greatly appreciated. Thank you!

JUGHNE

Picture of gas valve and of pilot burning, please.

Tneily

I took the pilot out of the furnace for easier viewing.

Tneily

I don't understand why the pilot wont stay lit. If the thermocouple is generating properly and the valve is good

ratio

Tneily said:

the valve is good

Is it? If the thermocouple is good and the valve still won't keep the pilot lit, well, that sounds like a bad valve to me.

Tneily

I changed the valve to a new. Same problem. So I changed it back to the old one

ratio

Hmmm... Did you measure the closed circuit voltage? That takes an adapter.

Oh, I found this to read. Maybe it'll help. There really aren't that many things to go wrong. It has to be one of them—even if you've already checked it, check again.

Tneily

I only have a multimeter to test with. I am about to replace the thermocouple again and hope for the best. I have found a comment saying that the poster had encountered bad thermocouples that tested good. I will let everyone know how it goes.

ratio

I'd be a lot more suspicious of a second bad thermocouple than a second bad gas valve.

And I put one of those thermocouple testers in my supplyhouse.com shopping cart for the next time I make a purchase. It looks like it'd be a handy service tool.

JUGHNE

Is the end of the T-Couple well into the flame?
Glowing red?
Some T-couple adaptors will seem to hold it in place but will go a 1/4 to 3/8" more bury.

Tneily

Thank you so much for the comments. I have the second consecutive thermocouple in as far as it can go. Still nothing. I don't know what to do. I've never had such a hard time trying to fix anything. Around the house or vehicle. No matter the level of difficulty. This has me feeling so beaten up

Tneily

Also
Yes, it's glowing red

Fred

That thermocoupler is way too far into the flame. Only the end 3/8's to 1/2" should glow cherry red. Having said that are you sure the other end of the thermocoupling is properly seated in the gas valve? Have you blown through the pilot tube to make sure it's not partially clogged with lint or dirt?

Tneily

Yes, I have done all of that. I actually bent the bracket after a while. Just out of desperation in looking for any possible remedy. Not that I really thought that it wasn't hitting right. But this had me questioning all logical explanation

ratio

Tneily said:

This has me feeling so beaten up

Don't. You've got a real head scratcher going on, that's for sure. Are you cold, is this something that has to get resolved ASAP, or can you take a break & come back to it? If it's got to get done to keep the house warm you might need to call a service outfit, but there're a lot of smart people here, I'm sure we can get it working.

Tneily

I can probably give it a bit before calling someone.

JUGHNE

Is the end squarely inserted into the gas valve?
Be sure there is no dirt in the gas valve receptor.
Also, I always clean the end of the t-couple by rubbing it on pencil erasure and then again on clean blue jeans.
Screw in with fingers, while moving tube up and down to be sure it seats all the way, you can feel when it bottoms out, then just a little tighten with tool. FWIW

Tneily

Yeah, I've made sure several times that the end was clean and properly seated.

Fred

I can't see where the dial on the gas valve is setting. Is it on "OFF" or "Pilot" ? It looks like there are only two settings on that valve. If so are they "ON" and "OFF"? The dial looks like it may be broken. Is it set correctly?

Tneily

No sir. It is set to off during the photo. But it has pilot and on, also.

Tneily

The newer one that I had swapped in and out is the same thing. Just looks a little newer.

Fred

Is there a 24V power source to that valve? Is it properly connected? Does it require any power to hold the internal pilot valve open? Does your 24V transformer test out OK?

Tneily

Yes there is a 24v power source properly connected. I have tested that source going into the control valve. But from what I understand. The pilot valve is not supposed to need anything more than what is provided by a good flame and thermocouple.

Fred

Do you still have the pilot/thermocoupler out? Does it need to be grounded? I'm at a loss

ratio

Did you try a(nother) new thermocouple with the new gas valve too? A double fault isn't very likely, but I think we're past the likely issues now!

HVACNUT

Is it a boiler or furnace?
I'm sure you're pressing and holding the red pilot button for at least a minute before letting go.
Is the flame stable?
For some reason, I can't upload your pics, so,
Is there an induced draft motor?
Is there excessive draft through the boiler or furnace? Whole house fan, or any large exhaust running?
Tight boiler room? Meaning too tight.

Tim McElwain

Did you follow the test that ratio referenced. That is my step by step procedure for testing completely including doing a combustion test.

Tim McElwain

If you have trouble with following the procedure give me a call at 401-437-0557 and I will walk you though what you have to do.

Tneily

Thank you to everyone for being so helpful. It turned out to be jus plain bad luck. I went and put the new valve back in. Then connected the newer of the new thermocouples. I must have tried a defective t couple that tested good. Before swapping the old valve back in. I knew that I didn't have the proper tools to do a true diagnosis. The thought of wasting $100 and still not get anywhere had me panicked. Thankfully I didn't try to return it to get my money back.
It took ten minutes to switch back and resolve the issue. Including the time checking for leaks.
Anyways. I wasted a lot of time by only havin a multimeter and trial/error to diagnose. But they say all is well that ends well. Thanks again to everyone who took the time to comment

Jamie Hall

And thank you for letting us all know how it turned out!

ratio

That's the way of it sometimes. Glad you got it figured out, & as Jamie said thanks for the follow-up.

jumper

A double whammy will get you every time.Usually there's a cascade effect. Mr. A misdiagnoses a problem so he makes the situation worse. Now Mr. B has to find two bad things.

I was certain that Tnelly's issue was draft.

newagedawn

sounds like the ignition module is bad

JUGHNE

I have never seen an ignition module for a standing pilot flame with old school Thermocouple.........have you?

Tim McElwain

An ignition module is designed for a system with a spark ignition pilot system which proves by miroamps not millivolts.

A thermocouple system has a pilot which is lit 24/7 and has no need for an ignition module. Two seperate systems.

j a_2

JUGHNE said:

I have never seen an ignition module for a standing pilot flame with old school Thermocouple.........have you?

That's a good one, me either

David37

Had the same problem with the pilot lighting and staying lit in my old RV. Cleaning the pilot orifice solved the lighting problem. Replaced thermocouple and still had a problem staying lit. Both new and old thermocouple gave 25-30 mv when tested. Lightly sanded the gas valve end of the thermocouple and gently scraped the female contact point in the gas valve with a phillips screw driver and the pilot lit and stays lit. The 30mv were not getting to the pilot light lock in coil.

smcmahon

@David37 You just saved me! I had the same issue and the flame was perfect, the thermocouple was new and it was in the flame perfectly, the gas valve was new, but it would not stay lit. I took the gas valve end out and sanded it like you said, then screwed it back in and it worked!! I’ve been trying to figure this out for 2 days. Thank you!!