Gas and Oil Home Heating Furnaces - fan motor turns on then off, on then off

have bryant heater 1984 air worked fine all summer,woke up on morning, heard fan motor turn on then off, on then off, took panel off heard clicking noise was told to replace relay circuit board it solved the clicking noise but fan motor still tries to turn on then off. took fan motor out hooked up to direct source motor runs perfect.

Need Help: thanks

Sounds like the relay board wasn't the problem anyway. The clicking was probably the fan relay starting and stopping the fan. The new board may have a qiueter relay but you still have the original problem. Did you change the thermostat recently? It might help to remove the wire from the R terminal of the furnace control circuit and that will isolate the thermostat from the circuit. If it still cycles, it is a furnace problem, if it does not, it is a thermostat or wiring problem. In heating mode, the thermostat does not control the fan. It is controlled by a thermostatic switch in the furnace or a time delay switch. In cooling mode, the thermostat controls the fan.

i removed the R terminal of the furnace control circuit and it still tries to cycle isolating the thermostat. if its a furnace problem where do i start.

Next we should know what triggers the fan in heat mode. Is it a time delay or is it a temperature control. If you could give us the model number maybe I could find a parts breakdown online. You could follow the blower leads and see exactly where they go. It may help to find the source of the power. It sounds like a time delay that is acting up or a shorted low voltage wire.

model # 394GAD024075

i'll check leads from motor to see where they go.

Thanks