Will pilot stay lit if thermocouple is bad? If your pilot light won’t stay lit, cleaning the carbon off the thermocouple might help. It’s designed to determine whether the pilot light is lit and then subsequently signals the gas valve to open. The job of the thermocouple is to keep the pilot lit. The thermocouple can do this because, in its probe, it contains two different metals, and a … The suggestions in this blog should help you fix these issues or at least help you understand the cause of the problem. After years of use, your thermocouple may have a buildup of carbon deposit, which affects its ability to function. Issue #1: Bad thermocouple A furnace thermocouple is a safety feature that regulates gas flow to your system based on whether or not the pilot light is on. If the pilot valve is closed the main valve would not open. Pilot does not light or stay lit after knob is released - Check carefully that gas to appliance is on and that the valve is in the correct (pilot) position and fully depressed when lighting. The pilot can go out for a number of other reasons, however, so if you're having trouble getting the pilot to stay lit , the thermocouple may not be at fault. The thermocouple, which operates as a safety device, turns the gas supply off when the pilot light goes out. Seattle Pioneer: This unit is a standing pilot. According to the check list posted on the unit, it says that if the thermocouple has been changed and the pilot light will not remian lit, the next item is the valve body. If the pilot is staying lit but the burners won't light the thermocouple is likely toast. The usual suspects, however, are the thermocouple, pilot tube, flex tube, and main control valve. A standing pilot gas valve has two inner valves, one for the pilot light and one for the main valve. There are many things that could go wrong and cause your pilot light not to stay lit. They are dependent on one another, totally. Its not putting enough voltage through to the valve to tell it its lit. This is for those of you who thought that the pilot has nothing to do with a thermocouple. The thermocouple was used to hold the pilot valve open. It consists of a heat sensor connected to a solenoid; when the sensor is not heated by the pilot flame, the solenoid closes the gas supply line. Replaced the thermocouple--same result. 1. Usually if the thermocouple is toast the pilot doesn't even stay lit. Replace it with something made this century. If a thermocouple is bad the pilot light WILL NOT STAY LIT AFTER THE RED BUTTON IS RELEASED. Nothing lasts forever, and when the thermocouple wears out, the pilot won't stay lit and your appliance won't work. Tested for power at the transformer--OK. 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