Display shows COd or COLD, spa may run pumps but not heat normally.

Safety first: Ensure the spa is not powered off in freezing conditions.

• Allow gradual heating: COd may appear when the spa is first filled with very cold water. Allow the heater time to raise the temperature.
• Use cover: Keep the Aquaterra cover closed and latched to retain heat.
• Verify sensor accuracy: If COd appears when water is warm, the temperature sensor may be misreading and should be tested or replaced.

COd is usually informational. If the spa never exits this mode or does not heat, have the heater and sensor checked.