Spa does 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 opening the control pack or accessing wiring.

Steps to diagnose no-heat condition:

• Confirm set temperature: Ensure the set temperature is higher than the current water temperature and that the spa is not in Economy/Sleep mode.
• Check for heater indicator: When heating is called for, the control panel should show a heat icon or indicator. If not, the control logic or sensors may be at fault.
• Verify flow: Ensure strong water flow through the heater by feeling for movement at the heater return. Clean filters and bleed air if needed.
• Test heater element (advanced): With power OFF and wires removed from the heater terminals, measure resistance across the heater element. An open circuit indicates a failed element that must be replaced with a Strong Spas-compatible heater.
• Inspect heater relay: Burn marks or clicking without heat may indicate a failed relay on the control board, requiring board repair or replacement.

When to call a technician: If you are not comfortable testing high-voltage components, or if the heater relay/control board is suspected, contact a professional.