Furnace Thermal Coupler

The thermocouple is a safety device located by the pilot light on your furnace.

Furnace thermal coupler.

If it accumulates soot it can give off a faulty reading and shut off the furnace. This device generates a small electric signal to keep the gas valve open when the pilot is on. In fact the problems that affect gas furnaces typically involve the furnace s thermocouple the pilot light or some component of the electrical system. Honeywell home cq100a1039 u cq100a1039 replacement thermocouple for gas furnaces boilers and water heaters 30 inch 4 7 out of 5 stars 80 9 31 9.

Natural gas and propane burn cleaner than fuel oil and most gas furnaces present fewer operational difficulties than oil burners do. You can test it with a multimeter. Most gas furnaces use either a flame sensor or a thermocouple often referred to as a thermal coupler both are safety devices that sense the presence of a flame and control the flow of gas to the appliance accordingly. If the pilot lights but won t stay lit the thermocouple is probably bad.

Fortunately cleaning a thermocouple is a repair most handy homeowners can do themselves.