Often asked: How To Test A Water Heater Thermocouple?

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.

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.

How do you read a thermocouple with a multimeter?

Select the ohms or resistance option on your multimeter. Place one test lead on the side of the thermocouple and the other to the end that screws into the gas valve. If the thermocouple has proper continuity, a small resistance reading should be visible on the multimeter.

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How do I know if my thermocouple is working?

Take the two leads from the meter and touch them —the meter should read zero. Once this check is done, turn the meter back to volts. For the actual test, turn on your flame source, and place the tip of the thermocouple into the flame, leaving it there until it is quite hot.

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.

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.

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.

What causes thermocouple to fail?

Changes in temperature can cause regular expansion and contraction in metal, which will cause thermocouples to weaken over time. After enough time, metal fatigue can cause a thermocouple to break. If thermocouples start to give out unusual readings, it may be suffering from metal fatigue.

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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.

Can a thermocouple work intermittently?

a safety device that has started to go bad, or has failed permanently. In this client’s case, the thermocouple was initially working intermittently, and then finally failed. This allowed the gas to flow long enough to heat up the thermocouple and generate some electrical current flowing back to the gas valve.

How do I know if my thermocouple is accurate?

To determine the initial accuracy of a thermocouple, you simply determine the greater of the two tolerances given. Note that standard and special tolerances for thermocouples are determined using the same method. Multiply 300°C by ±0.0075 which gives ±2.25°C.

How long does a thermocouple last?

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.

How do you bypass a thermocouple?

To bypass the thermocouple:

  1. Move the tilts switch wire aside.
  2. Remove your thermocouple from the heater using an 8mm wrench.
  3. Pull the valve housing aside using your 13mm socket wrench.
  4. Remove the valve using your pliers.
  5. Put your thermocouple back into position.

Can you 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.

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