No Hot Water: Water Heater Troubleshooting

How to diagnose and repair a faulty atmospherically-vented, gas-fired water heater. Common problems and how to fix them.

Example tank is a John Wood 40 gallon: Model AV40N
Same tank as A.O. Smith 40 gallon: Model GCRL 40

Status Light Codes
Normal Flashes:
• 0 Flashes Indicates Control Off/Pilot Out.
• 1 Flash Indicates Normal Operation.
• A continuous light indicates that the gas control
valve/thermostat is shutting down.
Diagnostic Flashes:
If the water heater is not working, look for the following
diagnostic flashes after lighting the pilot.
2 Flashes Indicates Thermopile Voltage Low
4 Flashes Indicates Overheat Failure
5 Flashes Indicates Sensor Failure
7 Flashes Indicates Electronic Control Failure
8 Flashes See “Status Light and Diagnostic Code
Troubleshooting Chart.”

Troubleshooting Chart: https://www.manualslib.com/manual/743692/A-O-Smith-Gas-Water-Heater.html?page=33

Related Videos:
Control Valve Replacement
https://youtu.be/5f6UFwRlXr8
Thermopile Replacement
https://youtu.be/1VIvEqVbt14
Thermopile Voltage Test
https://youtu.be/mtbn3FtMqCM

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Thermopile 100112328: https://geni.us/tglX2B
Thermopile Assembly 100112330: https://geni.us/p4gHRaE
Control Valve 9007884005: https://geni.us/ZJJkIB
Control Valve WT8840B1000: https://geni.us/2Kj3p

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