Display shows COL or COOL, heater does not run and water temperature is significantly below set point.

Safety: Ensure the spa is filled and all drains are closed before heating.

• Allow warm-up time: After a refill, it can take 12–24 hours for the spa to reach set temperature. Leave the cover on to retain heat.
• Verify circulation: Confirm that the circulation pump is running and that water is moving through the heater return.
• Check set temperature: Make sure the set point is above the current water temperature.

If COL persists for more than 24 hours and the water does not warm, there may be a heater or sensor issue requiring further diagnosis.