Display shows HTR or HEAT FAIL; spa does not reach set temperature even though pump runs.

Danger: Heater circuits carry high voltage. Only work inside the control pack if you are qualified. Always turn off power at the breaker and verify with a meter.

• Verify set temperature: Ensure the set point is higher than current water temperature.
• Check for error codes: Look for accompanying flow or sensor errors (FLO, Sn1, etc.) and resolve those first.
• Inspect heater connections: With power off, open the MAAX control pack and check that heater terminals are tight and free of burns.
• Measure heater resistance: Disconnect heater leads and measure resistance across the element. An open circuit indicates a failed heater.
• Confirm voltage: With power on (by a qualified person), measure voltage across heater terminals when the system calls for heat. No voltage indicates a control or relay issue.
• Replace failed part: Replace the heater assembly if the element is open, or the control board if the relay is not supplying power despite a heat call.