Odd suburban furnace problem...any help out there? Couldn't find a similar thread!

[101scout]

OK, this problem is more annoying than anything. I have a 78 Excella 500, full-timer. I'm not sure what Suburban model it is, but this is what's happening. I turn the thermostat on, fan comes on, furnace ignites, trailer heats up, furnace cools off and fans shuts off. pretty basic, right? Trailer cools off, temp setting kicks in and the whole thing repeats - everything works fine, and THEN!! Once and a while, for no discernible reason, the fan will not stop running after the furnace has cooled off. It'll run for hours if we're gone, or I let it. It is maddeningly intermittent. It seems more like a thermostat thing to me, or am I off track? Anyone have any clues?? As long as I'm home and it's acting up I just control it by turning the thermo off and on, and I'm in WA, so it's not too cold, but we're having a cold snap and my main concern is the tanks and pipes not getting the heat they need to keep from freezing!!

[Janets Husband]

This is a quote from the Suburban Tech Manual.

"4. If the fan continues to run after the thermostat is satisfied and the burner goes off, the fan switch or the time delay relay is defective and needs to be replace. If the fan comes back on after a short period of time (within one minute) and cuts off and on, replace the fan switch. "

Sounds like you have an intermittent problem in this circuit. Schematics and parts lists are available.