In the spring and fall when the heat and air are off the blower on the furnace will kick on and blow cold air. It has started doing it now with the heat on. After the temp has been reached and the blower kicks off, a while later the blower will kick on and blow cold air but the temp on the thermostat is at the correct temp. The furnace is a Janitrol and is 14 years old.

What is the model # of the furnace?

The model number is GMPN080-4. Serial number 96018 26194. Any help would be great. Thanks.

It sounds like either a problem with a limit circuit component or the circuit board. How long have you experienced this situation?

About a month