What does error code 4 flashes mean on a A.O. Smith water heater?

Temperature exceeded (ECO). The water got too hot and the energy cut-off (ECO) activated.

Can I fix A.O. Smith code 4 flashes myself?

Start with these safe checks: Turn the gas control knob to OFF and turn the main gas supply to the heater OFF. A.O. Smith's repair is replacing the gas control valve/thermostat. Call a qualified technician.

When should I call a technician for code 4 flashes?

A.O. Smith's repair is replacing the gas control valve/thermostat. Call a qualified technician. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

A.O. Smith Water Heater Error Code 4 flashes: Temperature exceeded…

What 4 flashes means

The water got too hot and the energy cut-off (ECO) activated.

Likely causes

Gas control/thermostat failure

Safe first checks

Turn the gas control knob to OFF and turn the main gas supply to the heater OFF.

When to stop

A.O. Smith's repair is replacing the gas control valve/thermostat. Call a qualified technician.

Checked against: A.O. Smith Residential Standard Gas Water Heater Service Handbook: diagnostic flash codes. Codes can differ by model and year, so confirm with your owner's manual.