| Not heating? | Circuit Breaker/Fuse | 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. |
| Igniter | 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. |
| Cycling irregularly? | Thermostat | 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? | Blower Motor | 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? | Control Board | 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. |
| Thermostat | 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? | Flame Sensor | 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. |
