FAQ: How To Test A Thermocouple On A Water Heater?

How do I know if my thermocouple is bad on my water heater?

If the pilot lights but the flame goes out as soon as you release the button after holding it for 60 seconds, then the thermocouple is bad. It’s possible to replace the thermocouple without removing the burner assembly, and many repair people do this.

How many millivolts does a water heater thermocouple need?

A healthy thermocouple should read between 20 and 30 millivolts in an open circuit test. If the reading is below 20 millivolts, the pilot may have difficulty staying lit.

How do you clean a thermocouple on a gas water heater?

Clean the thermocouple – using the emery cloth sandpaper, sand the ends of the thermocouple and then give it a finishing touch with the lint-free cloth. Hopefully, you can get to the ends of the thermocouple without having to detach it from the assembly, but you may have to do that.

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How do you reset the thermocouple on a water heater?

Find the thermal switch on the manifold door. Push the small button in the middle of the thermal switch to reset it. Restart the gas water heater by following the lighting directions printed on the side of the water tank.

What are the symptoms of a bad thermocouple?

Failed Thermocouple Symptoms

  • Signs of contamination on the tube, e.g. discoloration, cracks, or pinholes.
  • Signs of wear or corrosion of the wirings, e.g. missing insulation or bare wire.
  • Physical damage to the connectors which can have an effect on the reliability of the test reading.

Can you bypass a thermocouple on a water heater?

Realistically, you have just disabled the thermocouple, but you can also reach in and unclip it from its holding bracket where it meets the pilot light. In most cases it will be held on with a gravity clip, but some are held on with a screw that must be removed with a small screwdriver.

Will a pilot light stay lit with a bad thermocouple?

A thermocouple senses the heat of the pilot and allows gas to flow to the burner. A bad thermocouple will shut off gas to both the pilot and the burner so the pilot light won’t stay lit.

How do you check if a thermocouple is working?

If the thermocouple is working, you should be able to measure 30 to 40 millivolts of voltage at the connection end of the tube when the pilot flame is on. You can test this yourself using a multimeter, but you may need a helper to keep the pilot flame burning while you do it.

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Can thermocouple be too long?

The length of a thermocouple has no effect on its measurement accuracy or its ability to transfer the signal to the instrument. In other words, thermocouples do not experience “voltage drops” or power loss along its length as a high current power line might possess.

Can I clean a thermocouple?

The best way to clean your thermocouple is to use either a piece of steel wool or the coarse side of a sponge to gently clean off any soot or other remnants. You can use a pencil eraser to clean between the threads of the screw that connects the thermocouple to the control valve of your system.

How long does a thermocouple last on a water heater?

All things considered, the question remains, “How long should my thermocouple last?” The answer to that question is that it depends on the application. In an ideal environment, that length of time can be indefinite.

Why does the pilot on my water heater keep going out?

Why does the pilot light on my water heater keep going out? Your water heater pilot light keeps going out due to issues with the heater’s thermocouple or access to combustible air.

Can you replace a thermocouple yourself?

The No. 1 cause of pilot lights that won’t stay lit is a worn-out thermocouple. It’s easy to replace and a new one costs $5 to $10. Then unfasten the three nuts that hold the thermocouple and the two gas tubes to the valve.

What do you do if your pilot light won’t stay lit?

How to Light Your Furnace’s Pilot

  1. Make sure the thermostat is in heat mode.
  2. Locate the pilot valve.
  3. Always turn the valve knob to the off position and make sure to wait at least several minutes for any residual gas to clear away.
  4. Get your match ready.
  5. Once the pilot stays lit, turn the pilot valve to the on position.
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How much does it cost to fix a thermocouple?

The thermocouple is an apparatus that senses whether the pilot light is lit and triggers the gas control valve. Repairs typically cost about $150 to have it done professionally, though a new thermocouple itself only costs about $20 on average.

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