John Wood electronic gas water heater displays E015 and the burner cycles rapidly on and off

Safety: Turn off power before adjusting sensors.

• 1. Check thermistor placement: Ensure the temperature sensor is fully inserted into its well and secured. A partially inserted sensor can cause erratic readings.
• 2. Use thermal compound: If recommended by John Wood, apply a small amount of thermal grease to the sensor to improve heat transfer in the well.
• 3. Inspect for scale: Heavy scale buildup can cause uneven heating. Drain and flush the tank to remove sediment. For severe scale, professional descaling may be required.
• 4. Control replacement: If the sensor is correctly installed and in spec but E015 persists, the control board may be misreading temperature and should be replaced.