Spa will not heat, water stays cold but pumps run normally and no error code is displayed

Safety first: Turn off power at the GFCI breaker and verify no voltage before opening the control pack or heater connections.

• Check heater indicator: With power on and spa calling for heat, confirm that the heater icon or indicator light is on. If not, the control pack may not be energizing the heater.
• Inspect heater terminals: With power OFF, remove the cover over the heater terminals. Look for burnt wires or loose screws. Tighten connections as needed.
• Test heater element: Disconnect heater wires and measure resistance across the heater terminals. Typical values are 8–15 ohms depending on wattage. An open circuit indicates a failed element.
• Check for manual reset: Some heaters have a small red reset button on the heater tube. Press firmly to reset if tripped.
• Replace heater: If the element is open or the tube is leaking, replace the complete Master Spas heater assembly compatible with your control pack.
• Control pack issue: If the heater tests good but never receives power, the control board relay may be faulty and the control pack may need replacement.