AO SMITH SIGNATURE SERIES GAS WATER HEATER Flashing 4 Times

Gas Control Valve (Thermostat Assembly)

The 4-flash code signifies that the water temperature has exceeded the safety limit, triggering the Energy Cut Off (ECO) switch. This failure usually stems from a stuck internal solenoid or a faulty temperature sensor inside the valve body that failed to shut off gas flow at the set temperature. Since the ECO is a non-serviceable safety component within the valve, the entire control unit must be replaced.

SKU: 100112338

PEX Lined Dip Tube

A deteriorated or broken dip tube causes cold water to enter near the top of the tank rather than the bottom. This results in the thermostat at the bottom sensing cold water and running the burner continuously, potentially leading to localized overheating and an ECO trip (4-flash error) due to thermal stacking.

Gas Control Valve Component Kit (Pilot Assembly)

While less likely to cause an over-temperature condition, a compromised pilot assembly with a failing thermopile can cause erratic voltage signals to the gas control valve. In some logic boards, electrical noise or fluctuating millivoltage can be misinterpreted as a sensor out-of-bounds error, though the valve itself remains the primary suspect.