Upon starting the heat cycle the inducer motor spins up then shuts down it does this sometimes 3 or 4 times before the burners lite. Sometimes even after the burners lite it seems to shut down prematurely.
I have replaced the flame sensor and the air pressure switch to no avail.
York furnace. model – gy8s080a12uh11c
Video of issue. Problem starts at 30 second mark.
Best Answer
First off, it is the draft inducer motor that is turning on then shutting off, not the blower. There is no possibility that it is the flame sensor or the pressure switch since neither items had been called for yet. Order of operation: 1 thermostat calls for heat 2 inducer motor is called for and starts spinning 3 draft is proven via the pressure switch. If the pressure switch was bad the motor would just keep spinning with no ignition 4 igniter will ignite 5 gas valve will open and burners will ignite 6 flame sensor will complete circuit to ground via flame rectification. If it doesn’t sense flame it will stay lit for about 3 seconds then go out. 7 blower will come on. Your furnace only got to step 2 so the problem is before that. Check for voltage at the inducer motor. Best to use alligator clips and see if voltage drops out when the motor disengages. If voltage stays constant the problem is in the motor. If voltage drops to 0 then your problem is elsewhere. Jumper the W and R thermostat terminals at the circuit board to eliminate the thermostat or thermostat wires as the problem. If it is still happening then the problem is either the circuit board or a loose wire between the circuit board and the inducer motor.