The spa will not heat; the water stays cold even though the jets run and the set temperature is high.

Safety first: Turn off the power at the GFCI breaker and verify no voltage is present before testing the heater.

• Confirm demand for heat: Set the temperature several degrees above the current water temperature and ensure the spa is not in Economy or Sleep mode.
• Check for heat indicator: Many Lifesmart topside panels show a heat icon when the heater is commanded on. If the icon is on but the water does not warm, suspect the heater circuit.
• Test heater resistance: Disconnect heater wires and measure resistance across the heater element. Infinite or zero ohms indicates a failed element.
• Inspect high-limit: Reset any manual high-limit, if present, and ensure the sensor is properly seated.
• Replace heater assembly: Drain the water below heater level, remove unions, and install a new OEM-compatible Lifesmart heater assembly. Refill, bleed air, and test.