Spa will not heat, water stays cold even though pumps run and no error code is displayed.

Safety first: Turn off power at the GFCI breaker before testing heater circuits.

• Verify settings: Check that the spa is in Standard/Ready mode and that the set temperature is above current water temperature.
• Check for heat call: When the spa calls for heat, the heater indicator on the topside should illuminate. If not, the control may not be commanding heat.
• Test heater voltage: With a qualified person and power on, measure voltage at the heater terminals when there is a call for heat. Full line voltage should be present. If not, suspect the control board.
• Measure heater resistance: With power off and heater disconnected, measure resistance across the heater element. Replace the Arctic Spas heater assembly if open or out of spec.
• Check circulation: Ensure the circulation pump is running and that there is strong flow from the heater return.