Display shows OHH or HH, spa shuts down completely, no heat, pumps may be disabled until reset.

Safety first: Turn off power at the GFCI breaker immediately. Do not continue to run the spa until the cause is identified.

• Allow cooling: Leave the cover open and let the spa cool for several hours.
• Inspect heater area: Open the equipment bay and carefully feel (when cool) around the heater manifold for signs of discoloration, melting, or scorching that indicate overheating.
• Verify flow: After cooling, restore power and observe whether the circulation pump is running and water is moving strongly from heater return jets.
• Bleed air: If the spa was recently refilled, bleed air from pump unions to ensure the heater is not running dry.
• Sensor replacement: If OHH appears immediately on startup with cool water, the high-limit sensor may be defective and should be replaced with a Clearwater-compatible sensor.

Persistent OHH errors can indicate a dangerous heater or control board fault. If the heater is suspected of dry firing or the relay is stuck, contact a professional spa technician.