How to Replace a Flame Sensor Heater

Shut off both power and, if applicable, gas to your furnace. Face the front of your furnace and remove the front panel with a screwdriver. If you don’t see screws, then it’s held in by metal clips.

Look at your furnace’s burner compartment. A panel may protect the compartment. Remove it to gain access to the flame sensor. The flame sensor sits vertically in the blower compartment, typically on the lower-left side. It’s comprised of a thin metal rod with a small piece of porcelain attached. It has a horizontal piece on the end of it.

Remove the flame sensor. The flame sensor is usually held in place by either a screw on top or bottom. Sometimes a clip also holds it in place. Pull the flame sensor up and out once you have loosened it from the blower compartment. Disconnect the cable that connects into the sensor. Pay attention to how the sensor was in place.

Connect the new flame sensor to the appropriate wire. Place the new sensor in the old flame sensor’s location, exactly how the old flame sensor was positioned. The sensor should simply drop into place; you shouldn’t have to fight with it. Once in place, secure it with a screw or the clip.

Close your furnace by reattaching the blower compartment panel and front panel. Turn on both the gas and electricity. Turn your thermostat up so that the furnace will kick on. Watch your furnace. If it starts up and continues to run, then everything is working. If it suddenly shuts off, either the flame sensor isn’t installed correctly or another problem exists. If the flame sensor is secured by a screw or clip and it was positioned in the same way as the previous flame sensor, you have another problem with your furnace.