Display shows COOL; spa indicates water is significantly below set temperature and may run pumps without heating yet.

Safety first: Ensure the spa is filled above all jets and suctions before running pumps.

• Allow warm-up time: After a refill, it can take many hours for the heater to raise water temperature. Leave the cover closed to retain heat.
• Verify set temperature: Confirm the set temperature on the topside is higher than the current water temperature.
• Check heater indicator: Ensure the heater icon or indicator light is on when heating is expected. If not, check for other error codes (FLO, OH, etc.).
• Inspect filters and flow: If COOL persists and water does not warm, clean filters and verify circulation pump operation to ensure the heater can run.