How To Replace And Maintain A Furnace’s Thermocouple

If your furnace's pilot light is no longer staying lit, you'll have to replace the thermocouple. This sensor connects to the furnace's pilot light, and its job is to measure the voltage of your furnace. If the thermocouple is broken, your furnace will unable to operate properly. Thankfully, this part is easy to replace on your own by following these furnace repair steps.

Gathering Tools & Materials

Before you can get started, you'll need to gather the following items:

  • Adjustable wrench
  • Pliers
  • Sanding block
  • Sandpaper
  • Vacuum cleaner
  • Clean cloth
  • Replacement thermocouple

Anything you don't have can be purchased at a local home improvement store.

Removing The Old Thermocouple

Shut down all power going to the furnace, and then open up the access panel. Next to the furnace's pilot light, you will find a thin, long rod that has two clips attached to it. This part is the furnace's thermocouple. Detach these clips by pulling on them gently. Use your adjustable wrench or pliers to loosen all of the nuts connecting the thermocouple to the bracket. You should then be able to slide the furnace's thermocouple off the bracket it was secured to.

Inserting The Replacement Thermocouple

Insert the brand new thermocouple onto the bracket by replacing the nuts. You will then reattach the clips so that it is connected to the furnace's pilot light. Use the clean cloth for removing the dust in the furnace's interior, or use your vacuum cleaner if it is really dirty. A furnace that is clean will be more efficient, so it is best to do this now while the access panel is open.

Relight the furnace's pilot light, and then close the access panel. Turn the furnace on and verify that everything is working correctly.

Maintaining A Thermocouple

You'll need to make sure the thermocouple remains clean if you want to maintain it. You can do this by using your sanding block and sandpaper to remove buildup on the thermocouple as soon as it is noticeable. The buildup will have a white appearance to it, which is actually carbon. It will eventually cause your thermocouple to not function properly if the carbon is never removed. It also helps to use a cloth to wipe down inside the furnace every now and then.

If you have never worked on a furnace before, these steps may seem intimidating to you. Consider hiring a HVAC repair company in your area instead. They will be able to swap out the thermocouple or you, and guarantee the work in case something does go wrong with the thermocouple afterwards.