Display shows FLO and heater will not start; solar pump does not run or shuts off quickly.

Safety first: Turn off power to the Fafco controller and any booster pump at the breaker before opening plumbing or electrical enclosures.

• Check pool filter and baskets: Clean the skimmer basket, pump basket, and backwash or clean the main pool filter. Low system flow will trigger FLO on the Fafco solar controller.
• Verify valves: Ensure the solar supply and return valves to the Fafco solar panels are fully open. A partially closed valve will reduce flow.
• Inspect booster pump (if equipped): Restore power and briefly turn the system on. Confirm the Fafco solar booster pump starts and runs smoothly. If it hums but does not spin, the pump motor or capacitor may be failing.
• Check flow switch: Locate the flow switch or paddle sensor in the Fafco plumbing manifold. Inspect for debris or scale around the paddle. Clean gently and reinstall, ensuring correct flow direction.
• Reset and test: Restore power, clear the FLO code by turning the controller off and back on, then run the system and verify stable flow and normal operation.