Display shows OH or OHH and spa shuts down; water feels excessively hot near heater return.

Safety: Turn off power at the GFCI breaker and open the cover to allow the spa to cool. Do not enter the water when OH is displayed.

• Allow cooling: Let the water temperature drop below 100°F (38°C) before further testing.
• Clean filter: Remove and thoroughly clean the Jacuzzi filter cartridge. Run the spa briefly without the filter to see if OH returns.
• Check circulation: With power restored, verify that water is moving steadily from the circulation return jet. If there is no visible flow, the circulation pump may be failed or air-locked.
• Inspect sensor placement: Ensure the temperature sensor is fully inserted into its drywell or plumbing tee on the heater manifold and that the cable is not pinched or damaged.
• Verify set temperature: Confirm the set temperature on the topside control is not accidentally set too high.

If OH recurs quickly with good flow and a normal set temperature, the temperature sensor or control board heater relay may be faulty and should be tested and replaced by a technician.