I have a 1985 vintage Empire gravity direct vent wall furnace in out cottage mode # DV-235-3SG. Once the unit runs for a while and the room comes up to temp. the burner shuts off, but the blower keeps trying to cycle on and off - it makes an electrical sparking sound which causes interfence with nearby radios and tvs. This goes on for about 2-3 minutes each time the furnace completes a cycle. Seems like it is something in the blower control module? Any suggestions?

In your furnace you have a thermodisk that turns the furnace blower on when the temperature rises to a point that the disk is preset at. There is a diferental of maybe 20 to 25 degrees between the tempatures that turns the blower on and what turns it off. Over the years this disk loses some of it tension and gets to the point that this diferental and the burner on temperature both drop. Your disk is probably turning off too soon and the risidual heat in the heat exchanger is heating the disk back up to the point of turning the blower back on and then off again as it cools.

This disk in hidden beneath the outer cover It will have two wires attached to it. The temps will be printed on it. These disks should be found at most heating and air conditioning companies.