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. After years of use, your thermocouple may have a buildup of carbon deposit, which affects its ability to function. Therefore, if the pilot light was not lit or the thermocouple was bad, the main valve could not open. They are dependent on one another, totally. Seattle Pioneer: This unit is a standing pilot. Its not putting enough voltage through to the valve to tell it its lit. The thermocouple can do this because, in its probe, it contains two different metals, and a … 1. Replaced the thermocouple--same result. Odd though. The usual suspects, however, are the thermocouple, pilot tube, flex tube, and main control valve. If the pilot valve is closed the main valve would not open. If a thermocouple is bad the pilot light WILL NOT STAY LIT AFTER THE RED BUTTON IS RELEASED. 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. 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 suggestions in this blog should help you fix these issues or at least help you understand the cause of the problem. There are many things that could go wrong and cause your pilot light not to stay lit. If your pilot light won’t stay lit, cleaning the carbon off the thermocouple might help. Replace it with something made this century. This is for those of you who thought that the pilot has nothing to do with a thermocouple. When a thermocouple fails, the pilot light won't stay … If pilot ignites but does not stay lit after knob is released, then the problem is with the thermocouple not generating enough voltage to the valve. Everything looks good and I too think it could be the gas valve that is gone bad. If my Thermocouple is bad will my pilot light stay lite. The thermocouple, which operates as a safety device, turns the gas supply off when the pilot light goes out. The thermocouple was used to hold the pilot valve open. Nothing lasts forever, and when the thermocouple wears out, the pilot won't stay lit and your appliance won't work. The job of the thermocouple is to keep the pilot lit. Usually if the thermocouple is toast the pilot doesn't even stay lit. 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. 45 year old Pioneer heater. It’s designed to determine whether the pilot light is lit and then subsequently signals the gas valve to open. 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. 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