If it is either defective or dirty, it will not be able to detect a flame. Your furnace’s flame sensor monitors the burner, detecting whether a flame is present. Starting and then stopping shortly after? If it appears the thermostat is the issue, replace it. Use a multimeter to check for continuity. The contact that controls the blower motor on your thermostat may be stuck closed, causing the blower motor to run continuously. If the relay that controls the blower motor has failed, it will continually send voltage to the motor.

The control board regulates the amount of voltage that reaches each functioning part. If the motor runs but air doesn’t move, the connecting belt has probably broken. If it does, but isn’t running, the motor has likely failed.

Test to see if power is reaching the motor. If this doesn’t seem to be the case, then the connecting belt may have simply broken. Your blower motor may have completely burnt out. If this does not stabilize the unit, you may have to replace the thermostat. If your thermostat has an adjustable calibration scale, adjust the heat anticipator. Your thermostat might be adjusting incorrectly, causing the furnace to cycle on and off too often. If it isn’t cracked, use a multimeter to test for continuity. Check the part for cracks, if it is then replace the igniter. The furnace’s igniter might either be cracked or faulty. If it has blown, you will need to replace it. Try resetting your furnace’s circuit breaker. Most likely, either the electrical system providing your furnace’s power has shorted or the power switch has blown. If you're looking for help fixing your Armstrong Furnace, look no further! Our comprehensive Armstrong Furnace Troubleshooting guide will explain common issues, provide tips, and show you how to read your model's error codes.

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