A. O. Smith 4 flashes
A. O. Smith water heater 4 flashes: water temperature too high
Short answer
Four flashes means the gas control valve detected water that was too hot and shut off both the main burner and the pilot. A. O. Smith's corrective action is to relight the pilot to confirm the code, then replace the gas control valve.
Four flashes is an overheat code. The temperature sensor in the gas control valve saw the water get hotter than it should, and the valve shut off the burner and the pilot for safety.
Because the pilot goes out, you will usually only see the four flashes right after relighting it.
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.
If you smell gas, do not relight or reset anything and do not touch electrical switches. Leave the building and call your gas utility from outside.
What to do
- Relight the pilot following the instructions on the heater's label and watch the status light.
- If you see four flashes again, turn the gas control knob to OFF and turn off the main gas supply to the heater.
- Call a technician. A. O. Smith's chart calls for replacing the gas control valve and thermostat.
Why the valve is replaced
The high limit is built into the gas control valve. When it trips, it is a sign the valve's temperature control is not working properly, so the valve is replaced rather than reset.
Repair or replace the heater?
On a newer tank, a new gas valve is a sensible repair. On a tank ten years or older, compare the repair quote with the cost of a new heater before deciding.
Common questions
Is 4 flashes on an A. O. Smith water heater dangerous?
It means the water got too hot, which is a scald risk. The safety has already shut the heater off. Leave it off and have the gas valve replaced.
Can I just turn the temperature down to fix 4 flashes?
No. The overheat safety tripped because the valve's temperature control is suspect. Turning the dial down does not fix that.
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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) |