My furnace pilot light will not stay lit. I can light it and depress the pilot switch for 2 minutes. But, once I let go of the button, the pilot immediately goes out. Does my thermocouple need replacing?


Yes, either the thermocouple is going bad, it's not getting heated, or something is wrong with the controller. The most likely of those is that the thermocouple needs to be replaced. The button you press to light the pilot bypasses the thermocouple. When you release the button, the thermocouple ensures that unburned gas doesn't get released by shutting off the gas when it's not heated by the burning pilot light.

  • +1. Note there's no easy way to test the thermocouple, but since those commonly fail, it is the first thing to try. – Bryce Oct 29 '13 at 2:15
  • The thermocouple may just need to be cleaned. Or there may be an issue with the gas valve. Thermocouple can be checked with a mulimeter to see if it is faulty. Proper reading should be above 25 millivolts – Mnc123 Jan 5 '14 at 9:46

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