furnace doesn't shut off

[popgun2k]

I have a Comformaker gas furnace.After it has completed its heating cycle and starts its coolin down,t continues to blow cold air,and wont shut off like it should.I have to turn down the thermostat to shut off.This doesnt happen every time though,but just once in a while which baffles myself and a few furnacemen I've had look at it.This is not good,especially if you go out of town for a while and your blower fan keeps going and blowing cold air when its -40 outside.Any suggestions woould be appreciated

[a46geo]

Popgun 2K,

I too am new to the forum here, but I will welcome you anyway. First of all, the blower is only circulating the air in the house, it doesn't manufacture "cold air". Moving air just feels cooler. If you have an outdoor intake to the cold air return, you will draw in a small amount of outdoor air, just close the damper until the problem is fixed.

Many people with allergies and high end air cleaners will leave their furnace fan on constantly, all year long, in order to get the maximum

Your problem needs to be corrected, but it isn't a critical issue. benefit from the filtering system.

Many motor manufacturers CLAIM a motor will last longer if it remains on. In extreem cold, when the furnace cycles a lot, it may actually be cheaper to leave the motor on always play. This is because of the excessive amp draw (electric current and heat) generated to start an electric motor from a dead stop.

Now for the problem. The electronic or mechanical gizmo that controls the fan operation (which ever it is) needs to be changed. This may be an electric or electronic relay, a L4064 type fan control or a cam-stat control. It is obvious that whatever is supplying power to the fan is sporadically sticking.

Hope this helps.

George