Display shows FLC or FL2 and spa may not heat; flow error even when pump is off

Safety: Turn OFF power at the GFCI breaker.

• Locate the flow switch: Find the flow switch in the plumbing near the heater manifold. It will have two small wires going to the control pack.
• Inspect wiring: Follow the wires from the switch to the control pack. Look for crushed insulation, bare wires touching, or moisture inside the connector.
• Disconnect and test: Unplug the flow switch connector from the control board. Restore power briefly. If the FLC code changes to FLO or clears, the switch is likely stuck closed.
• Replace the flow switch: Turn power OFF again. Drain water below the switch level. Remove the old switch (unscrew or cut out if glued) and install a new OEM Michael Phelps/ Master Spas-compatible flow switch in the same orientation. Use proper PVC primer and cement if glued fittings are used.
• Refill and bleed: Refill the spa to the proper level and bleed air from the pump and heater unions.
• Restore power and verify: Turn the breaker ON and confirm that FLC is cleared and normal heating resumes.

If FLC remains even with the flow switch unplugged, the control board’s flow input circuit may be shorted and the control pack may need replacement.