Heater has power and display, but will not fire when there is a call for heat

Safety First: Turn off gas and power before removing panels.

• Verify setpoint: Ensure the temperature setpoint is higher than the current water temperature and that the correct mode (POOL or SPA) is selected.
• Check pump and flow: Confirm the circulation pump is running and that the heater's pressure switch is being satisfied (often indicated by a status light).
• Inspect safety circuit: Using the wiring diagram, check continuity through the safety string (pressure switch, high limits, rollout). Any open device will prevent firing.
• Observe ignition sequence: With panels in place, call for heat and listen for blower start, igniter glow, and gas valve click. If sequence stops early, the corresponding component or sensor may be at fault and should be tested and replaced as needed.