Heater display shows SF and will not run; blower does not start.

Safety first: Disconnect power at the breaker. Do not bypass safety switches.

• Check water flow: Ensure the pool pump is running and valves are open. Low flow can open the pressure switch and trigger SF.
• Inspect high limits: Locate the high limit switches on the heat exchanger header. Some models have manual reset buttons; press gently to reset if tripped. If they trip repeatedly, there may be a flow or scaling issue.
• Check pressure switch: Verify the pressure switch tubing is not kinked or clogged. Inspect the switch wiring and terminals for corrosion.
• Wiring inspection: Follow the safety circuit wiring (pressure switch, high limits, fusible link) and ensure all connections are tight and not burned.
• If SF persists: The safety circuit or control board may be faulty. Have a technician test continuity of each safety device and replace the failed component.