Furnace Thermocouple Replacement

A thermocouple on a gas furnace has one end connected to the gas valve and the other connected to the pilot light. When it senses that the pilot has been extinguished, the thermocouple shuts off the valve to stop the flow of gas. If the pilot on your furnace will not stay lighted, and there hasn't been an interruption of gas service into the home, you may have a malfunctioning thermocouple. You can purchase a new thermocouple at most hardware or home improvement stores for less than $20, according to 2011 prices. Take the old thermocouple to the store with you to ensure that the replacement is the correct length.


Tools Of The Trade
Standard screwdriver
Phillips screwdriver
Nut driver
Adjustable wrench
Thermocouple

Step 1:
Shut off the gas supply to the furnace by locating the closest shutoff valve and turning it completely clockwise.

Step 2:
Locate the pilot light access panel, which is usually toward the bottom of the furnace in the front. Remove the fasteners that secure the access panel using a standard screwdriver, Phillips screwdriver or nut driver, depending on the type of fasteners used. Turn the screws counterclockwise to loosen them.

Step 3:
Unfasten the old thermocouple from the gas valve and the pilot light using an adjustable wrench to turn the fittings counterclockwise.

Step 4:
Install the new thermocouple by threading the fittings on both ends clockwise onto the valve and the pilot light by hand. Tighten the fittings completely using the adjustable wrench.

Step 5:
Restore the gas supply to the furnace and relight the pilot light. Replace the access panel.