Display shows OH or OHH, spa shuts down, pumps may run briefly then stop, water feels excessively hot near heater outlet.

Safety first: Turn off power at the GFCI breaker. Do not use the spa until the cause of overheating is identified.

• Remove spa cover and allow cooling: Leave the cover open for several hours to let heat escape. Verify water temperature with an independent thermometer.
• Check water level and filter: Ensure proper water level. Remove and clean the filter cartridge. Run the spa briefly without the filter to see if the OH code clears after cooling.
• Open jets and diverter valves: Make sure all jets are open and diverter valves are not fully directing flow away from the heater return. Restricted flow can cause localized overheating.
• Inspect temperature and high-limit sensors: Locate the sensors on the heater tube (often two probes or thermistors). Check for secure mounting and good contact with the heater tube. Loose or corroded sensor connections can cause false OH readings.
• Reset high-limit (if manual reset type): Some Artisan control packs use a manual reset high-limit switch on the heater. With power off and water cooled, press the red reset button if present.

If OH returns quickly with normal water temperature, the temperature sensor or high-limit sensor may be faulty and should be tested and replaced. Persistent overheating with very hot water may indicate a stuck heater relay on the control board, which requires professional service.