Display shows OH or OHH, spa shuts down, jets may stop, and water feels excessively hot near the heater outlet.

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

• Remove spa cover: Allow the water to cool naturally with the cover off to release trapped heat.
• Check water level and filters: Verify proper water level. Remove and thoroughly clean the Dynasty Spas filter cartridge. Run the spa briefly without the filter (after water cools and power is restored) to see if the OH code clears.
• Inspect circulation: With power restored and water cooled, confirm that the circulation pump is running and there is strong flow from the circulation return. Weak or no flow can cause localized overheating.
• Sensor check: Inspect the temperature and high-limit sensors threaded into or clipped onto the heater tube. Ensure they are fully seated and their cables are intact. If OH appears immediately on startup with cool water, a sensor may be faulty and should be replaced as a matched pair.
• Heater relay suspicion: If the heater continues to heat even when the spa is in standby or set to a low temperature, the heater relay on the control board may be stuck closed. In that case, the control pack should be serviced or replaced by a qualified technician.