Gas Water Heater: Pilot won't stay lit
If your pilot light will not stay lit, it is important that you take steps to fix it immediately. Several problems can shut off the pilot-a failed gas supply, lack of combustion air due to a clogged vent or a vent draft that blows out the pilot. A missing, crooked or blocked vent draft hood can cause a vent draft. Also, if the vent pipe cap on the top of the vent pipe on the roof is blocked or missing, wind can go down the pipe and blow the pilot out.
Another common problem causing the pilot to go out or not stay lit is a failed thermocouple (pilot generator). The thermocouple in your water heater keeps the pilot lit by sending a low current electrical signal to keep the gas valve open. If the thermocouple fails, it doesn't send the signal to the gas valve and the gas valve shuts off, extinguishing the pilot.
When lighting the pilot, you press and hold the pilot button to supply gas to the pilot until the pilot heats up enough to generate the signal to keep the gas valve open on its own. If the pilot light goes out when you release the button, you'll likely need to replace the thermocouple because it isn't sending the signal to the gas valve to keep the gas valve open.
Replace the water heater thermocouple
The thermocouple monitors the pilot light. It detects whether your pilot light is lit by generating a small electrical current powered by the heat of the pilot flame. The gas valve won't open if it doesn't sense the small electrical current produced by the thermocouple because it assumes the pilot light is off. Replace the thermocouple if it doesn't detect the pilot flame.
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