Furnace won't keep running

[lostagain]

Took it all apart, again. Everything checks out. I have it narrowed down to this: run good with end cover off. Shuts down the gas valve within a couple of minutes once I put cover on. That is the housing cover that goes in front of the igniter/flame sensor. I don't think it affects air flow because it would trigger the sail switch and it doesn't. Combustion air is isolated from forced air side, and doesn't get affected. The combustion air wheel is good and clean, so are intake and exhaust.
Maybe the increased heat after putting the cover on affects something?
I'll look at all the wiring. I am wondering about the igniter wire. Looks good but maybe the increased heat makes it not conduct anymore, telling the board there is no flame?
There is another Suburban furnace in the horse trailer. I could swap igniter wires. I could swap control boards too, to make sure I don't have a board issue.

I'd like to find the problem. I'd hate to give up and buy a new furnace...

JC

[Dave5Cs]

Yep swap the boards to see. I will bet it is the board. a little burnt resister or diode would do it and you can't tell by looking at it.

[thomasinnv]

The 2 main components prone to the type of thermal failure you are describing are the control board and the solenoids. You would be surprised just how sensitive those little solenoids can be. I was working in a shop outside sacremento last year and one of the techs working on a furnace on the bench was pulling his hair out becuase no matter what parts he threw at it he could not get it to stay lit lomger than about 30 seconds or so. I casually walked by and slid the exhaust tube on it and he couldn't stop shaking his head and saying "i cant believe thats all it was"

Sent from my SM-G930T using Tapatalk

[lostagain]

I'll go with thomasinnv and Clifford's advice and order a gas valve. I'll let you know when I put it in.

JC

[lostagain]

Bingo!

I got a new gas valve, and it works really good now. I guess the valve solenoids, in spite of testing good on the bench, would overheat and let go after a few minutes running inside the hot cabinet.

I now have a pretty good idea of how a RV furnace works. lol.

Thanks all for the help.

JC

[Dave5Cs]

Just in time for summer JC LOL

[Gary Hatt - Publisher BCM]

Glad all is well now JC.  Now you can jump in your bus and start hitting the NorthWestern Bus Nuts rallies up there just over the border.  Check out our rally page or the NWBN website for the ones they have scheduled so far.  http://busconversionsstore.com/rally-news/

[oldmansax]

Bingo!
I now have a pretty good idea of how a RV furnace works. lol.

Thanks all for the help.
JC

That's the way it works! by the time I find out everything I need to know about my problem, I have a new problem! 

TOM