Spa will not heat; water stays at or near ambient temperature even though pumps run and set temperature is high.

Safety first: Turn off power at the GFCI breaker before opening the equipment compartment.

• Confirm settings: Verify the set temperature is above current water temperature and that the spa is not in economy or sleep mode.
• Check for flow: Ensure the circulation pump is running and that you feel water movement at the heater return.
• Inspect heater: Look for signs of corrosion, burn marks, or leaks around the heater tube and unions.
• Reset high-limit (if equipped): Some heaters have a manual reset button on the heater housing. Press it gently until it clicks.
• Measure heater voltage (advanced): With a multimeter and power on, a technician can verify that the heater terminals receive proper voltage when heating is called for. Voltage present but no heat indicates a failed heater element.

Heater replacement involves electrical connections and should be performed by a qualified technician if you are not experienced with spa wiring.