How to Change a Thermocouple on a Furnace
Essentially, thermocouples are a type of safety device on modern furnaces. They detect the temperature of the pilot light and cause the gas valve to close whenever the pilot light goes out in order to prevent gas build up or explosions. These devices are not foolproof, however, and they occasionally need to be replaced in order for the furnace to work properly. How a thermocouple is replaced can be broken down in just a few steps. Does this Spark an idea?
Things You'll Need
- New thermocouple unit
- Screwdriver
- Wrench
- Lighting device for the pilot (a fireplace match)
Instructions
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Preparation
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1
Shut off the gas to the furnace following the specific manufacturing instructions on your model. Some furnaces have buttons that turn off the gas, while others have knobs that need to be turned. Wait at least five minutes for residual gas to disperse before proceeding.
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2
Remove the panels that hide the thermocouple with a screwdriver or wrench, depending on how they have been secured. Some models of furnace will have more than one panel that needs to be removed in order to access the thermocouple.
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3
Identify the thermocouple unit. The thermocouple should be next to the pilot light, will have a copper lead and will be screwed to the gas line connection.
Replacement
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4
Unscrew the copper lead of the thermocouple from the gas line connection. The thermocouple also may be secured to a bracket by a screw. If so, disconnect the thermocouple from this bracket as well.
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5
Slide the thermocouple out of its position and put the new thermocouple in its place. You should have the copper side (tube) facing down.
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6
Screw the copper lead of the new thermocouple to the gas line connection. If the thermocouple is meant to be secured to a bracket, secure the thermocouple to the bracket, as well.
Finishing
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7
Screw the panels that hide the thermocouple back into place.
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8
Turn on the gas.
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9
Relight the pilot light following the manufacturer's instructions for your specific model of furnace.
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1
Tips & Warnings
If the connections or parts around your thermocouple are dirty, clean them after taking out the old thermocouple and before inserting the new one. This is also a good time to look for any other parts that may be damaged or worn and to inspect the functioning of the pilot.
Make absolutely sure that you do not begin replacing the thermocouple prior to shutting off of the gas, as you could breathe in gas and be asphyxiated or cause an explosion. If you smell gas prior to beginning the replacement, hold off on the work and call in a professional to see if you have a gas leak, making sure you're out of the house.
