Display shows “COOL”; spa will not heat to set temperature and may run pumps intermittently.

Safety first: Ensure power is supplied through a properly functioning GFCI.

• Allow warm-up time: After a refill with cold water, it can take many hours to reach set temperature. Leave the cover closed to retain heat.
• Verify set temperature: Confirm the set temperature on the topside control is higher than the current water temperature.
• Check heater operation: Listen for the click of the heater relay and feel the heater return area for gradual warming over 30–60 minutes.
• Sensor check: If the water is clearly warm but the display reads much lower, the temperature sensor may be out of calibration and should be tested or replaced.