Display shows OH or OHH and spa shuts down; water may feel excessively hot.

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

• 1. Remove spa cover and let it cool: Leave the cover open to allow heat to escape. Wait until water temperature drops below 104°F (40°C).
• 2. Check water level: Ensure the water level is above all suction fittings and skimmer openings. Low water can cause poor flow and heater overheat.
• 3. Clean or bypass filters: Remove all PDC Spas filter cartridges. Rinse thoroughly with a garden hose from top to bottom. For testing, run the spa briefly without filters (never leave it long-term this way) to see if OH clears, indicating a flow restriction from dirty filters.
• 4. Bleed air from circulation pump: If the spa was recently drained/refilled, air may be trapped. Loosen the pump union on the circulation pump slightly until water seeps out, then retighten. This helps purge air and restore flow.
• 5. Verify pump operation: With power restored, observe whether the circulation pump runs when the spa calls for heat. Listen for humming without water movement (indicating a seized pump) and check for visible flow at the return jets.
• 6. Inspect heater manifold: With power OFF, check for kinks, closed slice valves, or debris in the heater inlet/outlet. Ensure all valves are fully open.
• 7. Sensor check: If flow is good and filters are clean but OH persists, compare the displayed temperature to a thermometer. If the reading is much higher than actual, the temperature or hi-limit sensor may be faulty and should be replaced.

Call a technician if: The spa repeatedly overheats despite good flow and clean filters, or if the heater manifold shows signs of melting or scorching. This may indicate a stuck heater relay on the PDC Spas control board.