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CapnJustice · 12-31-2016, 05:54 AM

In the front furnace, fan starts in response to thermostat setting, never gets any heat, then fan shuts down within about 15 seconds. Can turn off, wait, and replicate.

Rear furnace working just fine so it's not a general propane delivery problem. I'm on the road and it's cold! Anyone with ideas?

manderson2228 · 12-31-2016, 07:18 AM

I'd check fuses first. Then the sail switch.

Then I would follow this troubleshooting guide if the previous two don't work.

http://www.rvforum.net/miscfiles/Furnace_Trouble-2.pdf

Gary RVRoamer · 12-31-2016, 08:28 AM

I don't think the furnace fuse or the furnace sail switch could cause that problem. The fan would not run at all if the furnace fuse was blown, and the sail switch prevents ignition of the gas burner but doesn't ever shut off the fan.

15 seconds of fan time sounds like the burner chamber purge cycle. The fan runs for about 15 seconds to clear fumes from the burner before starting the ignition cycle. Maybe your furnace ignition board isn't taking the next step after the purge cycle? Still seems odd, though, because the fan should continue to run as long as the thermostat is calling for heat. Even if the burner never lights. My other thought is that the thermostat (or the zone controller on a multi-zone system) is not keeping the "heat needed" signal line active. It's a +12v signal to the furnace and the furnace is supposed to run as long as it is present, and stop 15-20 seconds after the signal disappears.

CapnJustice · 12-31-2016, 05:30 PM

Quote:

Originally Posted by CapnJustice

In the front furnace, fan starts in response to thermostat setting, never gets any heat, then fan shuts down within about 15 seconds. Can turn off, wait, and replicate.

Rear furnace working just fine so it's not a general propane delivery problem. I'm on the road and it's cold! Anyone with ideas?

Pulled the cover off of the furnace burner area. There is a probe right at the front. All I had to do was to wiggle one of the spade connectors to it and voila' -- it works. I'm guessing some corrosion had built upon the connection. Ran fine all day.

Thanks for all the feedback.