Dirty or Defective Flame Sensor | Causes & Prevention
3 minutes read

Dirty or Defective Flame Sensor

Published by Steven Weiland

One of the most common causes of an otherwise fully operative furnace failing to produce heat is a problem with the flame sensor.

What a Flame Sensor Does

The flame sensor is a safety feature that is designed to protect your family and your home from dangerous conditions that can arise after the gas is ignited. It is composed of particular metals that create an electrical current in the presence of a flame. The sensor is designed to detect whether or not the fuel is being burned properly by the last burner in the group of burners.

If the flame is steady at the last burner, this indicates that the proper ratio of fuel and air is being distributed to each of the burners, and a safe burning environment is assumed. When no flame is detected, it could mean that any one of the burners is not working properly. The flame sensor is designed to signal the control board, and the control board shuts down the system.

Because any system can produce an occasional false reading, your furnace may try to restart two or three times, and then turn off for a period of several hours, or even permanently until the condition is addressed and the control panel is reset.

Possible Causes of a Flame Sensor Malfunction

There are two possible reasons a flame sensor will not relay the proper information to the control board. The most common is that it is dirty. Because burning fuel of any kind produces trace amounts of moisture, over prolonged exposure to these conditions, metal will rust. Since your sensor is made of metal, rust can build up, preventing proper sensing of the flame.

The other possible issue is a cracked insulator or otherwise defective sensor. It may be that a short has developed in the electrical component, stopping communication with the control board.

What to Do

The best thing to do if you hear your furnace starting and stopping two or three times, and it still doesn’t begin to cycle, is to call on our expert technicians at Heatmasters. We can clean or replace the defective sensor, safely restoring warmth and comfort to your home or business. Count on experience. Count on quality. Count on Heatmasters!

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