Display shows OH and spa shuts down pumps and heater; water feels excessively hot.

Safety first: Do not use the spa when OH is displayed. Turn OFF power at the breaker and remove the spa cover to allow cooling.

• Allow spa to cool:
  • Leave the cover off until water temperature drops below 38–40°C (100–104°F).
• Check circulation:
  • Clean filters thoroughly or run briefly without filters to ensure strong flow.
  • Verify that the circulation pump is running when the spa calls for heat.
• Verify temperature reading:
  • Use an external thermometer to compare actual water temperature to the displayed temperature.
  • If the display is significantly higher than actual, the temperature sensor may be faulty.
• Inspect heater relay:
  • With power OFF, open the control box and inspect the heater relay for welded contacts or burn marks.
  • If the heater continues to heat even when the control says it is off, the relay is likely stuck closed and the control board must be replaced.
• Replace faulty sensor or board:
  • If the sensor is out of calibration, replace the USSPA temperature sensor.
  • If the relay is stuck or the board misreads temperature, replace the main control board.