Plumbing Questions? Ask a Plumbing Expert.
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What is the brand and model number of your heater? does the gas control valve have 2 arrows (not a dial) to adjust the water temp? If so which LED's are lit when i doesn't work besides vacation?
Ok, the gas valve is telling you that the heater had an ignition error. Since it will start back up by cycling the power the most likely culprit is a dirty flame sensor. The flame sensor is positioned in the main burner flame (see attached picture for typical). You can clean off the metal rod of the sensor with steel wool or fine aluminum oxide sandpaper. Also vacuum out the burner chamber while you have it open. A stray rust flake can ground out the sensor and also cause a failure. Be careful that the sensor remains in the same position the spacing between the burner and the sensor is important
If you mean far left A & B plus the LED under the triangle then there is a problem with the gas valve and the only fix is to replace it
Do you have any more questions?