Pilot on furnace won't stay lit

[mthieme]

I replaced the thermocouple, but the pilot won't stay lit on my Rheem propane furnace. It will stay lit for a little while, don't know exactly how long. Do you think I got a bad thermocouple?
This morning I got it going and when it works, it works normally.
Last season I had to replace the board; the unit would kick on, get up to temperature then shut down - the fan wouldn't kick on. I've replaced the thermocouple once before a long time ago. Furnace is 10-12 years old.

 

[SS MAYFLOAT]

Re: Pilot on furnace won't stay lit

Make sure the Themocouple (TC) is directly in the flame. Some are bi-metal and will produce a few millavolts, then there are some that the pilot flame itself creates continuity to show proof of pilot. Also check to make sure that the TC is clean and tight if it is the type that goes into the gas valve. If it is not clean and tight, the millavolts is not enough to jump the gap.

 

[Laddies]

Re: Pilot on furnace won't stay lit

There is a very good chance if you remove the gas gun and then the pilot and main head you will find there is carbon in the supply lines to them.

 

[mthieme]

Re: Pilot on furnace won't stay lit

There is a very good chance if you remove the gas gun and then the pilot and main head you will find there is carbon in the supply lines to them.

There was some soot/carbon hanging off the end of the little pipe where the gas comes out for the pilot. Is this the gas gun? I knocked it off and noticed that the flame touched the TC which it wasn't doing before. This made a difference. It really didn't want to light before that. I can get it going now and I can feel the TC tube being warm to the touch now so I think that end is okay (?).
The furnace has been running for an hour or so now. I can see the pilot still lit.
I'm waiting for the unit to kick off so I can monitor the pilot.

 

[SS MAYFLOAT]

Re: Pilot on furnace won't stay lit

Soot being carbon is an insulator that can and will prevent the proper heat transfer for the TC to generate the proper millavoltage.

 

[mthieme]

Re: Pilot on furnace won't stay lit

I'll see what I can get apart and clean.
The furnace just kicked off finally.
The pilot is still lit.
The flame is more orange instead of blue.


SHAZBAT.
15 minutes later the pilot is out.

 

[mthieme]

Re: Pilot on furnace won't stay lit

I took off the tube that goes from the valve to the plate that shares the TC.
The end up by the TC was sooted up but nowhere near clogged. I blew it out with compressed air and got all the soot off. Put it all back together, and lit her up. The shape and color of the pilot are completely different...hopefully for the better. I just got the pilot lit a couple minutes ago. Hopefully it will last longer than 15 minutes. The tube was hard to blow through. The tube itself is about 1/4" diameter and has a brass cyndrilical fitting at the business end. I assume it has an orifice in it (?). If it were a clog, I would think 135psi from the shop air should have cleared it. Nothing came out when I blew in it other than the soot at the end.

 

[Laddies]

Re: Pilot on furnace won't stay lit

Sorry for not getting back but sounds like you have covered it without me. Let me know how you come out, my son went through the same thing with a 5 year old furnace and the dealer told him he either need a new gas valve or another furnace, I said something about it to a freind and he went up to the kids and fixed it in about 15 minutes.

 

[ne7800]

Re: Pilot on furnace won't stay lit

i hate pilot lights or just this reason thats why my furnace is electric ignition

 

[mthieme]

Re: Pilot on furnace won't stay lit

i hate pilot lights or just this reason thats why my furnace is electric ignition

Hmm. Wonder if there is a conversion kit?

Hopefully I'm good to go...it's still lit. Let's see if I wake up to a cold house or not.

 

[ne7800]

Re: Pilot on furnace won't stay lit

Hmm. Wonder if there is a conversion kit?

Hopefully I'm good to go...it's still lit. Let's see if I wake up to a cold house or not.

i bet there probably is

 

[mthieme]

Re: Pilot on furnace won't stay lit

After a little googling, a conversion kit doesn't look good. They do of course manufacture electric ignition units. Could be that the right mechanic could make it happen.
I'll give them a call later in the week.
Thanks for the idea.

Pilot is still lit.
Now, if I only had decent duct work...

 

[mthieme]

Re: Pilot on furnace won't stay lit

Special thanks to SS Mayfloat.
The thermometer is hovering right around the freezing mark and my family and I are warm.

 

[ne7800]

Re: Pilot on furnace won't stay lit

thats good news

 

[SS MAYFLOAT]

Re: Pilot on furnace won't stay lit

Special thanks to SS Mayfloat.
The thermometer is hovering right around the freezing mark and my family and I are warm.

Your welcome. Instead of doing a conversion, check on the newer high efficiency units. All of them have electronic ignition. To do the conversion would mean changing out the gas valve and adding a new control board. Could get pricey and plus it not being designed for it can and cause problems. Something that you don't want to happen when mother nature throws those "O" temps at us.

I installed a 90% efficiency unit for my brother in law. This past winter, his bill was lower than the previous year with his old furnace. The big kicker is that the gas rates jumped here by 18%. So even with the increase and new unit, his gas bill was lower by $20 to $30 a month.

BTW, it is a good practice to do a tune up on your furnace prior to heating season. Filter change, clean pilot & main burner, clean blower on the squirrel cage, and do a carbon monoxide test. The later can save lives and keep you healthier........Glad to have helped you.......SS

 

[Caveman Charlie]

Re: Pilot on furnace won't stay lit

Make sure your exhaust pipe/chimney is clean too. A bird can build a nest in there, or go in there and die, and cause all sorts of problems. The air intake needs to be free of restrictions as well!!!

On my travel trailer the little furnace seemed to burn a bad color and the exhaust fumes smelled like... bad combustion.After removing the furnace I found that the fresh air intake was almost completely plugged with wasp nests!!! I got a coffee can half full of wasp nest out of there!

Everything burns much cleaner and has a better color now.