It keeps cutting on and off. What could it be?

Thermostat, limit, pressure switch, vent, gas valve, aliens, draft inducer, blower motor, gremlins, wiring, plugged condensate drain, flame sensor, plugged condensate trap, etc, etc, etc. But most likely crazy alien gremlins that have moved into your furnace.

Now, that being said, can you give us a bit more info on exactly what your furnace is doing. If so, we will do our best to help.

PS. And yes, I'm a bit bored tonight.

I have Nordyne MGHA 075 AAFC-01 everything seams to work fine until when heat gets to temp furnice shuts down but don't come back on to cool down.Wheres my problem? Thank You.