Should a hole develop in the tip of a thermocouple after it is installed in a gas heater and lighted?

Question

I just replaced the thermocouple in my gas heater as the pilot wouldn't stay on after lighting. The old thermocouple had developed a hole in the tip and the tip was discolored when I removed it.

I checked the pilot today and it went off sometime today or yesterday. I noticed that the new thermocouple developed a hole in the tip and the tip was also somewhat discolored.

I relighted the pilot and it appears to still work fine.

Is the thermocouple suppose to develop a hole in the tip after being exposed to the pilot flame for a few days?

Edit: I have removed the thermocouple and it is not a hole, but just discoloring. I have cleaned the tip and reinstalled it.

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Answer 1

The Thermoucouple should withstand the heat of the pilot without damage. If it is still working you are ok but I would get a backup in case it fails. Thermocouples work with 2 dissimilar metals fused together and they create a small voltage when heated. If the junction of the 2 metals is damaged then the Thermocouple will not work. Some manufacturers call there Thermocouples Thermopiles I have used universal replacements and never had a problem as long as they screw in correctly.