||Your furnace’s fuse has blown, or the circuit breaker has shorted.
||Either reset the furnace’s circuit breaker or replace the blown switch completely.
||Either the igniter is defective or cracked.
||Check to see if the igniter is cracked and replace it If it’s not, test it with a multimeter to see if it’s defective.
||Your thermostat is likely not adjusting correctly.
||Use your thermostat’s adjustable calibration scale to adjust the heat anticipator. If this doesn’t work or isn’t an option, replace the thermostat.
|Not blowing hot air?
||Your furnace’s blower mower may be completely burnt out, or the connecting belt may have snapped.
||If the blower motor is receiving power but isn’t running, replace the motor. However, if it does run, it’s more likely that the connecting belt has snapped, replace it.
|Blowing too much air?
||The relay on the control board that regulates how much voltage is sent to the blower motor has failed.
||You will have to replace the control board.
||The thermostat contact that controls the blower motor function might be stuck in a closed position.
||You’ll have to use a multimeter to check for continuity if this appears to be the issue then replace the thermostat.
|Starting and then stopping shortly after?
||The flame sensor may not be able to sense the presence of a flame due to it being dirty or defective.
||If the flame sensor is dirty, use an abrasive pad to wipe it clean. If it’s defective, replace the flame sensor.