I have a '96 goodman janitrol mod#gmpn060-3 the problem is that it will cycle normally for an hour , maybe two, sometimes overnight ,but when it get to the end of it's heating cycle and the air starts to cool down,the blower stops for about a second and then the blower will stay on without the heat. the blower will continue running until you cut the power. if you leave the power off for about an hour or so and turn the power back the furnace will start and run normally , until it has another one of those fits. The furnace does have a blinking light and a chart for the codes: incorrect twinning=reverse primary wires incorrect polarity= reverse secondary leads My repair man has replaced two control panels,new thermostat,igniter,and a blower sensor. He can't seem to find out what the problem is and is recommending to just buy a new furnace. any ideas??