John Wood electronic gas water heater shows E005 and shuts down; tank is very hot to the touch

Critical safety: If water is extremely hot or you see steam at faucets, shut off power and gas to the heater immediately. Do not use hot water until the issue is resolved.

• 1. Allow tank to cool: Leave the heater off for several hours until the tank and water lines are cool to the touch.
• 2. Check thermostat setting: On the gas control, verify the temperature dial is set to a safe level (typically 49–54°C / 120–130°F). Reduce if set higher.
• 3. Inspect temperature sensor: Many John Wood electronic models use a thermistor inserted into a well on the tank. Disconnect the sensor and measure resistance; compare to the temperature/resistance chart in the service manual. Replace if readings are out of range.
• 4. Flush sediment: Sediment buildup can cause hot spots. Connect a garden hose to the drain valve, shut off cold water supply, open a hot faucet, and drain several gallons until water runs clear. Close drain, refill, and purge air.
• 5. Gas control replacement: If the ECO has tripped and will not reset, or if the burner continues to fire past the set temperature, replace the gas control valve/thermostat assembly. ECO devices are non-resettable on many models.

Warning: Overheating is a serious safety hazard. If you are unsure of the cause, contact a qualified technician.