A. O. Smith Water Heater 4 flashes: Overheat failure
Updated October 2026 · Sourced from A. O. Smith documentation
🛑 Turn it off and call a licensed pro
Four flashes indicate an overheat failure. The chart says high water temperature has activated the over heat sensor (ECO).
Is it safe to keep running? No. Turn it off and get it checked. The chart says to replace the gas control valve/thermostat. Call a licensed pro.
4 flashes at a glance
| Code / how it shows | Meaning | Applies to |
|---|---|---|
| 4 flashes Gas control valve status light flashes, then a pause | Overheat failure | A. O. Smith Direct Vent Residential Gas tank water heaters (Ultra Low NOx models) with gas control valve/thermostat status light |
Check this first
Only steps a homeowner can do safely. Do not open electrical panels or the burner area.
- Turn the temperature knob to a lower setting and be careful with hot water.
- Do not try to bypass the sensor.
🛑 Stop and call a licensed pro if
- The chart says to replace the gas control valve/thermostat. Call a licensed pro.
- You smell gas. Leave the house, do not touch switches, and call your gas utility from outside.
- Codes for flame failure, overheating, venting or the control board that return after one reset.
- Water leaking from the heater, the relief valve discharging, or scorching around the burner area.
- A carbon monoxide alarm sounds. Get everyone outside and call 911 or the fire department.
Safe first steps for any A. O. Smith code
- Write down the exact code shown on the controller or the number of status light flashes.
- Turn the water heater power off and back on (or press the reset button the manual describes) once. If the code comes back, stop resetting.
- Make sure the gas supply valve to the heater is open and other gas appliances in the home are working.
- Make sure the cold water supply valve is fully open and hot water taps are not partly closed.
- Look at the outside vent terminal for snow, ice, leaves or anything blocking it (look only).
Source: A. O. Smith Direct Vent Residential Gas Water Heater Installation Instructions and Use & Care Guide (Ultra Low NOx), Status Light Code, p. 21 and 30. Codes are series-specific, so your unit's own manual is the final word. Reviewed October 2026.
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Related A. O. Smith codes
2 flashes : Thermopile voltage low5 flashes : Sensor failure7 flashes : Electronic control failure8 flashes : Pilot or thermopile still active with the knob off03 : Incorrect DIP switch setting10 : Warning for the 991 code (air or exhaust problem)11 : Ignition failure12 : Loss of flame31 : Outlet thermistor failure32 : Inlet thermistor failure61 : Fan motor fault72 : False flame detection