Display shows COL or COOL, heater does not run and spa may run pumps to warm water slightly.

Safety first: Ensure the spa is filled and all plumbing is intact before running pumps in freezing conditions.

• Verify actual water temperature: Use a separate thermometer to confirm the water temperature.
• Allow warm-up: If the spa was just filled with cold water, allow the system to circulate; the code should clear as the water warms.
• Check sensor placement: Make sure the temperature sensor is fully seated in its well or threaded port and not exposed to outside air.
• Inspect sensor cable: Damage to the sensor cable can cause false low readings.

If COL persists with normal water temperature, the temperature sensor may need replacement.