Furnace Won’t Turn On With Faulty Flame Sensor


Upon arrival to this home, Approved Comfort technicians found a seven year old York furnace with a bad flame sensor. The technician replaced the flame sensor and cycled the unit to ensure it was operational.

If you had a bad flame sensor on your furnace, the burners will come on for about five seconds and then immediately go back out. This will not help your home get heat, so what can you do to try and fix it?

Fixing a Faulty Flame Sensor

The easiest way for you to fix this problem is to clean it with steel wool or a greenpad. You want to clean it as though you were giving it a light sanding; just enough to remove the accumulated buildup. Over time, that carbon buildup will prevent the sensor from detecting the flame.

When working properly, here’s what you should expect:

  1. The flame will pass over the sensor and produce a minor electrical charge
  2. That electricity is sent to the gas valve. The gas valve allows the gas to continue to flow.
  3. When the sensor doesn’t receive the proper flow of electricity, it can’t give the signal to turn on the gas. And when the gas doesn’t turn on, your furnace doesn’t heat.


If you’ve tried cleaning it and have not seen any results, it’s time to call in the experts. Approved Comfort Heating and Air Conditioning has been helping customers all over the Lake in the Hills area for 20 years. We strive to be the most desirable business to work for, and work with. When you call us, you can trust that you are getting the best heating service in the business!

For any and all furnace needs you may have, call Approved Comfort today!