Jacuzzi Runaway Heating / Thermostat Overshoot

Water overheats beyond the set temperature without showing an OH code; spa feels too hot.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Stuck heater relay on control board, Miscalibrated temperature sensor, Poor sensor contact with heater tube, Incorrect sensor placement

How to Fix / Troubleshooting

Safety: Turn off power and do not use the spa until the issue is resolved.

  • Verify temperature: Use an external thermometer to confirm actual water temperature.
  • Inspect sensor mounting: Ensure the temperature sensor is firmly attached to the heater tube or fully inserted into its well.
  • Power cycle: Turn power off for 5 minutes, then back on and monitor heating behavior closely.

If the heater continues to run past the set temperature, the control board heater relay is likely stuck and the board should be replaced immediately.

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Repair Difficulty

Professional Required 5/5

Required Part

Control Board
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