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.

Nothing lasts forever, and when the thermocouple wears out, the pilot won’t stay lit and your appliance won’t work. Secondly, how many millivolts should a thermopile produce? The normal millivolt output is 25 to 35 millivolts; on some, you may even get up to 35.

Diagnosing a Thermopile Problem Just like the thermocouple, the thermopile can be read with a multimeter to check if it’s the cause of the problem. Three hundred millivolts or higher voltage is a sign of a good thermopile. A reading below 300 millivolts would require you to replace the thermopile.

When it comes to your hot water heater, the pilot light heats up the thermopile. As this occurs, they produce a small voltage of electricity that passes over to the gas control valve. A pilot light can go out. When this happens, there is no electricity, so it shuts down the gas control valve until the light is relit.

They produce 750 millivolts when heated. depending on what it is in you may have to buy a adapter to test it.

The normal millivolt output is 25 to 35 millivolts; on some, you may even get up to 35. The other part of this safety pilot system is the electromagnet (power unit). It is if you will the LOAD and we can say the thermocouple is the SOURCE.

To bypass the thermocouple: Move the tilts switch wire aside. Remove your thermocouple from the heater using an 8mm wrench. Pull the valve housing aside using your 13mm socket wrench.

The flame should be adjusted to a soft blue flame, not roaring or lifting. The normal millivolt output is 25 to 35 millivolts; on some, you may even get up to 35.

The pilot flame should touch the thermocouple at a specific level. If the flame is blue and weak, and barely reaches the thermocouple, it needs to be stronger. If it extends well above the thermocouple, it’s too strong.

It’s Dirty. Soot buildup on the thermocouple may block the flame. Under constant exposure to a hot flame, a thermocouple wears down over time. Even a slight residue can make the thermocouple malfunction.

If you have a faulty thermocouple is the most common reason that your pilot light is malfunctioning. Over time your water heater will collect dirt, dust and other kinds of debris. Build up on your thermocouple can cause a malfunction. This is and easy fix, simply let it cool down and brush off the dirt or debris.

It costs $150 to $250 to replace a thermocouple. It checks to make sure the pilot light is on. It will shut the gas off if it’s not.

Universal Thermocouples. Universal thermocouples, as the name implies work on most water heaters. They are available online and in home supply stores for a reasonable cost. The length and the thread type are the two concerns when purchasing one.

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Whereas a J Type thermocouple is made up of iron and constantan, K type thermocouples are composed of a nickel/chromium alloy (chromel) and a nickel/aluminium alloy (alumel) which gives them much better protection against oxidation and acidity than the iron limbs of the Type J.