Heater cycles on and off frequently, with short run times and frequent restarts.

Safety first: Turn off power before accessing sensors or control wiring.

• Check setpoint: Ensure the set temperature is not set extremely close to current water temperature, which can cause rapid cycling.
• Improve water mixing: Make sure the temperature sensor (if remote) is installed in a well-mixed part of the plumbing, typically on the return line after the heater.
• Adjust flow: Increase pump speed or open valves to provide a more stable flow through the Thermeau heater, reducing rapid temperature swings.
• Sensor accuracy: Compare displayed water temperature to an independent thermometer. Replace the Thermeau water temperature sensor if readings are inaccurate.
• Consider control adjustments: Some models allow adjustment of differential or hysteresis; consult the manual or a technician to widen the temperature differential.