Display shows COOL, and the heater does not run even though the set temperature is higher.

Safety first: Ensure the spa is filled with clean water and GFCI protected.

COOL indicates that the water is significantly below the set temperature, and the system may delay heating until safe conditions are met.

• Verify water level and circulation: Confirm the proper fill level and that the circulation pump is running with good flow.
• Allow warm-up time: After a fresh fill with cold water, it can take many hours to reach the set temperature. Keep the cover closed to retain heat.
• Check mode: Make sure the spa is in Standard/Ready mode, not Economy or Sleep.
• Monitor for change: If COOL remains for many hours with no temperature increase, there may be a heater or sensor fault that needs diagnosis.