Display shows COL and spa will not heat above a low temperature setpoint

Safety first: Ensure the spa remains powered during freezing conditions to prevent damage.

• Check mode: On the topside control, verify the spa is in Standard mode, not Economy or Sleep. Refer to your Master Spas user manual for button sequences.
• Verify set temperature: Increase the set temperature to your desired level and wait to see if the heater engages.
• Allow time to warm: In very cold conditions, it can take many hours to raise water temperature. Keep the cover closed to retain heat.
• Sensor check: If COL persists even when water is warm, the temperature sensor may be misreading and should be tested and replaced if faulty.
• Control configuration: Some models display COL during initial cold start-up. If the spa does not heat at all, contact a technician to verify control pack programming.