I have a Bryant furnace plus 90 model #398AAW036060D. I just changed the blower motor. In the last five years I've changed the main board, inducer board, pressure switch, and cleaned the igniter the the the fan limit switch.

It was running well and then it got to where the inducer motor starts, burners light and run, and after the burners stop firing the blower motor runs. The furnace blows warm air. The blower stops and then the whole process starts again. What would cause this?


Normally the burners heat up the heat exchanger tubes. The blower motor circuit senses the heat and turns on the blower motor fairly quickly. As long as there is a call for heat (thermostat on), the burners and blower continue their merry operation. When thermostat opens, the burners quit immediately and the blower runs a short while to get the remaining heat from the heat exchanger.
Does your blower motor wait too long to start, or does it stay on too long? Or does the thermostat switch off too early? Or do the burners shut off too quickly? These answers will point to the faulty part.

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