Cleaning a Furnace Flame Sensor
If your furnace flame sensor has become dirty with build up, the furnace won't function properly. Keeping the sensor clean is simple and requires just a few tools when you follow these easy steps.
Step 1 - Turn Off the Power
Before you start playing working on the furnace, you need to cut the power. Turn it off at the breaker box for the safest operation.
Step 2 - Locate and Remove the Sensor
The sensor is typically attached towards the rear of the furnace. Look for a rod that is placed in the path of the burner. The sensor is held in place with one or two sheet metal screws attached to a bracket. Remove the screws to drop the sensor box from the bracket. Not all models will allow you to remove the sensor. You can still clean it; doing so will just require you to work in an odd position to access it.
Step 3 - Clean
Many people suggest you use sandpaper. While this is acceptable, it can damage the sensor. Emery cloth can be found at any hardware supply store. It will work much better. Gently scrub the sensor surface to remove any build up.
Step 4 - Reattach
Reattach the sensor and turn the furnace back on.