Suburban furnace not restarting
Furnace is a Suburban NT-16SE, and the thermostat is also a Suburban 161654 (at least it looks like that one; there's no model number on it that I can find). I took the burner out, and it has hardly any rust on it. The burner chamber looks clean, and the vents on the outside appear to be clear of debris.
Took the SMB out this week for a 2 nighter, and it was cold enough to use the LP furnace. First time really using it, other than briefly testing it when we got the van.
So I turn on the propane switch, and move the thermostat control to the middle of the range. Furnace fan kicks on, and after a few seconds, the burner fires up. Got the van nice and toasty in a few minutes.
Van warms up, and the thermostat correctly shuts the furnace off. After a while (15 minutes?), I notice it's getting cooler in the van again. Check the thermostat, yep, still set to middle of range. Wait about another 10 minutes, and it still hasn't turned the furnace on.
Turned the thermostat back to Off, and then back to the middle of the range. No fan, no heat. Tried this a few times, still no fan or heat. Turned thermostat back to Off.
After about 30 minutes, I try again. This time, the fan comes on, and then the burner fires up. Okay! Good!
Then the van warms up, and the thermostat shuts the furnace off. Then, as before, a lot of time goes by and the furnace won't come back on by itself. I have to wait quite a while with the thermostat Off and then try again. Sometimes it works, sometimes it doesn't. I took the cover off of the thermostat, and everything seems connected and moving as it should.
Back home today, I spent some time watching it work and trying to figure out the problem. All the wires seem secure, there's about 3/8 of tank of propane on the gauge, the thermostat coil moves as the temperature changes, but the furnace won't kick on after the first run. After waiting a while with the thermostat off, it will fire again. At least the problem is consistent!
I don't think it's the propane, but you never know. The tank was filled on the east coast, elevation about 300 ft. Now it's in New Mexico, and the elevations I've been trying to use the furnace at are between 3900 and 5300 ft. I did notice that when the burner is firing, the flame has a bit of yellow in it, but it had that at the low elevation, too.
Tomorrow, I'm going to try purging the air out of the LP tank, but I don't think this is the problem. After all, the furnace will fire the first time very easily. Also, with the propane switch off, the furnace fan will still start up. So I'm guessing that there isn't a propane sensor in the furnace.
Before I spring for a new thermostat, does anybody have any other ideas?
DesertBoat ...has been SOLD. Sad to have seen it go.