Gas and Oil Home Heating Furnaces - Forced air heater fan keeps running after burner turns off

The heater goes thru it's normal turn on cycle and provides heat. However when the controler turns off the flame the circulation blower keeps running and pumping cold air and does not turn off.

Does it never shut off? I know you've probably done this but check the fan switch on the t-stat and be sure it's in auto. If that's not it we'll check other things. What's the Make, M# and S# of your furnace?

This heater is in my 88 year father in law's moble home. So, I was only passing on what he told me. But, now I know that, in fact, the fan is in the manual mode because that is the only way the furnace will come on. Still don't have a mfr mod or SN.

You dont say if gas or oil here . But on most mobile home furnace . You have whats call a Klixon fan control. It is small and round there. You have to find out what the #### are on it and get a new one. Not hard to put in.;) ED

The heater is gas and I suspect you are right about that switch. I think there are two heat actuated switches one that turns the fan on at a certain temp and another that turns the flame off if the fan fails to come on. I suspect my father in law was having problems with the heater not staying on and found that if he turned on the fan manually it would work.

One of those temp actuated switches is a safety feature to keep the fan from running if there's no flame on the burner. That could blow gas fumes into the ductwork and the house. Not a good thing. :)

The other switch lets the fan draw residual heat out of the furnace after the burner shuts off. Mine runs for about 1 minute after the burner goes out.

I hope your dad keeps the filter clean there in the furnace. That Klixon fan control that they put on the mobile home furnaces there just break down a lot. You also said he put the fan to on so the furnace ran???????? Id look and see if the blower fan blades are clean and blowing like they should . If you have a dirt build up in the cup of the blades the blower wont blow what it should.
I dont think they have a 80 % or 90% furnace here dave

;) ED

It was all a false alarm. It turns out that my 88 year old Father in law got confused about the settings. When someone with more patience went thru the start up procedure, the furnace worked and cycled just fine.