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What you will learn from How to Test a Thermocouple with a Multi-Meter article:

 

  1. How not to guess if the thermocouple is bad
  2. Step by step procedure for testing a thermocouple with a multimeter
  3. What reading you should get if the thermocouple is good
  4. Lots of resource and related links to help you learn more

How to Test a Thermocouple with a Multi-Meter? So you have found the pilot light will not stay lit when you try to light the pilot light. You know you have gas and everything seems to be fine so what is the problem?

How to Test a Thermocouple with a Multi-Meter

You ask a friend and the friend tells you the thermocouple is bad.

So how do you test the thermocouple to see if it is bad or not? You will need a multi-meter that will read millivolts (most meters read small voltage like millivolts which is 1/1000th of a volt) and a source of fire such as a lighter or small torch. How to Test a Thermocouple with a Multi-Meter step by step:

How to Test a Thermocouple with a Multi-Meter

Thermocouple fits securely in the pilot burner (pictured above)

  1. Remove the thermocouple.
  2. Turn on the meter and set it to Ohms. Touch the two leads together from the meter and you should get a reading close to zero. With the leads apart you will read infinity. This is simply a test to check the meter for continuity. NOW TURN THE METER TO VOLTS.
  3. Start the flame and put the tip of the thermocouple in the fire.
  4. Ensuring the tip is nice and hot from the flame take one lead from the meter and put it on the shaft of the thermocouple and the other lead and put on the end of the thermocouple where it makes contact with the gas valve.
  5. If the reading is less than 25 millivolts replace the thermocouple as most standing pilot gas valves need 25 or more millivolts to keep the pilot flame lit.

How to Test a Thermocouple with a Multi-Meter

If you test the thermocouple with the multimeter and you get a reading above 25 then you have another issue. Always make sure the tip of the thermocouple is directly in the pilot flame. If the tip is in the flame, you have held the nob on the gas valve down for longer than a minute, the pilot flame is strong and steady, and the pilot still does not stay lit then you likely have a problem with the gas valve. Gas valves can not be repaired as per any manufacturer and need to be replaced. Good luck!

Use our handy calculator to see how many BTU's your natural gas appliances are producing:

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How to Test a Thermocouple with a Multi-Meter

Resource, Learn More HVAC and About the Author

To learn more about heating systems and HVAC use this resource.

See the About the Author page for information about the author of this article.

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