Display shows FLO or FL1 and heater will not run, circulation may be intermittent

Safety first: Turn off power at the breaker before accessing the equipment bay.

• Clean/remove filters: Remove all filters and run the spa. If FLO clears, replace or deep-clean the filters.
• Bleed air: Loosen the union on the circulation pump or heater inlet to release trapped air, then retighten.
• Locate flow switch: On many Master Spas models, the flow switch is installed in the plumbing line near the heater. It has two small wires leading to the control pack.
• Inspect flow switch: Check for kinks in the line and ensure the switch body is level and installed in the correct flow direction (arrow on body). Do not bypass the switch for normal operation.
• Test switch (for advanced users): With power OFF, disconnect the flow switch wires and measure continuity while water is flowing (pump on) versus off. It should close (show continuity) with flow. If it stays open, replace the flow switch assembly.
• Check circulation pump: If there is little or no flow, the circulation pump may be failing and should be replaced.