Display shows OH or OHH and spa shuts down; water may feel very hot near the heater or in the filter area.

Safety first: Turn off power at the GFCI breaker immediately. Do not use the spa until the cause is identified. Very hot water can cause burns.

• Remove cover and allow cooling: Open the spa cover fully to let heat escape. Allow water to cool below 38°C (100°F) before restarting.
• Check filters and flow: Remove and clean filter cartridges. Ensure all jets and suction fittings are unobstructed. Verify that the circulation pump runs smoothly when power is restored.
• Inspect around heater: With power OFF and equipment bay open, feel for kinks or closed slice valves on plumbing to and from the heater tube. All valves must be fully open.
• Restart and monitor: Restore power and watch the temperature reading. If the OH error reappears quickly while water is still cool, the temperature sensor or high-limit sensor on the heater manifold may be faulty.
• Check for stuck heater relay (advanced): If the heater indicator on the topside is on constantly, even when set temperature is reached, the heater relay on the control pack may be welded closed. This requires control pack repair or replacement by a technician.

If OH recurs after cleaning filters and confirming good flow, have a professional test the temperature and high-limit sensors and the control pack before further use.