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What to Do When Your Furnace Has a Dirty Flame Sensor

No one wants to be left without a working furnace on a cold day. If your furnace begins to start up, but then shuts back down right away, don’t panic. It’s possible you have a dirty flame sensor, which is simple to repair.

What is a Flame Sensor?

Every furnace has a flame sensor. When the furnace turns on, the gas valve opens and sends gas into the combustion chamber, where the burners are ignited by the pilot light. The flame sensor is a safety device that ensures the furnace will only run if a flame is detected when the gas valve is open. If your furnace were to run with no flame, dangerous gas buildup could occur. The flame sensor automatically shuts the furnace down if no flame is detected. 

Signs of a Dirty Flame Sensor

A dirty flame sensor is a common furnace issue. Carbon deposits, dust, and dirt tend to build up on the flame sensor over time. It’s especially common if the furnace is located in a basement, attic, or another area where there is a lot of dust in the air. The flame sensor is very sensitive, and if it’s dirty, it can read incorrectly and shut the furnace down.  

How will you know if your flame sensor is bad? The warning signs include:

  • Your furnace is short cycling
  • The flame sensor appears corroded
  • Cracked porcelain on the flame sensor

What to Do With a Dirty Flame Sensor

If you’re having a problem with your flame sensor, it’s best to call an HVAC technician to repair it. The best way to prevent the flame sensor from getting dirty is to schedule heating service each year. Cleaning the flame sensor is part of a regular furnace tune-up.

For assistance with your flame sensor or other heating repairs, contact us.