4 flashes = High-temperature lockout. The ECO (Energy Cut-Off) safety has tripped because tank temperature exceeded ~180°F. The unit is locked out until the ECO is manually reset and the underlying cause is addressed.
Diagnostic sequence
1. Verify the lockout
Wait 30 minutes for the tank to cool. Then attempt to reset (see below). If the ECO trips again immediately, an active fault is present.
2. Most common cause: thermostat stuck closed
The main thermostat (on gas units, integrated into the gas valve) has stuck closed, allowing the burner to fire even when the tank reached setpoint. Replacement is dealer-installed.
3. Heavy sediment / scale
Sediment at tank bottom can insulate the temperature sensor, causing it to mis-read tank temperature. Burner over-fires; ECO trips. Flush the tank.
4. Low water level
If the tank wasn\'t fully refilled after a drain/maintenance, the burner over-heats the partial tank water. Verify tank is full (open a hot tap; water should flow steadily without sputtering air).
5. Power vent fan failure (power vent models)
If the fan stops mid-cycle, exhaust backs up, heat doesn\'t leave, temperature spikes. ECO trips. Diagnose fan.
How to reset the ECO
- Wait 30 minutes for the tank to fully cool
- Turn the gas knob to "Off"
- Locate the ECO reset button (red button on the gas valve assembly)
- Press firmly
- Turn gas knob to "Pilot" → relight pilot → turn to "On"
- Monitor LED — if 4 flashes returns, underlying cause is active
If 4 flashes returns repeatedly
Don\'t keep resetting. Repeated ECO trips suggest a stuck thermostat or scaled tank — both potentially dangerous. Call State support or a State-authorized installer.
Bottom line
4 flashes is a safety trip — investigate the cause before resetting. Most common: stuck thermostat or heavy scale.