A. O. Smith 2 flashes
A. O. Smith water heater 2 flashes: weak thermopile
Short answer
Two flashes means the pilot is lit but the thermopile is not producing enough voltage to run the gas control. A. O. Smith says the thermopile is probably defective, though a weak pilot flame or loose wiring can cause the same thing.
On A. O. Smith gas water heaters, the status light on the gas control valve blinks once every three seconds when everything is normal. Two flashes is a warning about the power supply to the valve.
These valves have no electrical cord. A small device called a thermopile sits in the pilot flame and turns heat into the electricity that runs the valve. Two flashes means it is not producing enough.
These codes apply to standard atmospheric A. O. Smith gas tanks with a status light on the gas control valve. Power vent, condensing and tankless models use different codes, so check the label on your heater if the pattern does not match.
What causes 2 flashes
- A worn thermopile. The most likely cause, according to A. O. Smith's troubleshooting chart. Thermopiles wear out with age.
- A weak pilot flame. A dirty pilot orifice or low gas pressure makes a small flame that does not heat the thermopile enough.
- Loose wiring. The thermopile wires plug into the gas valve; a loose or corroded connection lowers the voltage.
What to do
Turn the gas control knob to OFF. A technician will usually check the thermopile's output with a meter, clean the pilot, and replace the pilot and thermopile assembly if needed. On many A. O. Smith models the pilot and thermopile come as one assembly.
The heater may keep working for a while, but a failing thermopile tends to get worse until the pilot will not stay lit. Fixing it early avoids a cold shower on the worst possible day.
Common questions
Can I keep using my A. O. Smith water heater if it flashes 2 times?
It may keep working for a short time, but the thermopile is likely failing. Plan to have it checked soon.
Is a thermopile the same as a thermocouple?
They do a similar job but are different parts. Many newer A. O. Smith gas valves use a thermopile, which produces more voltage to run the electronic control.
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Other A. O. Smith codes
| Code | Meaning |
|---|---|
| 0 flashes | Light off: pilot out or thermopile not yet warm |
| Solid red | Solid red light: pilot recently went out, thermopile cooling |
| 2 flashes | Pilot lit but thermopile output too low |
| 4 flashes | Water temperature too high (high limit tripped) |
| 5 flashes | Temperature sensor (thermistor) failure |
| 7 flashes | Gas control valve failure |
| 8 flashes | Thermopile still producing power with the knob off (pilot valve may be stuck open) |