Display shows FLC (flow closed) and heater will not engage; sometimes occurs even with pumps off.
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power at the GFCI breaker before touching any wiring or components.
- Power cycle the spa: Turn the breaker OFF for 60 seconds, then ON. Observe if FLC clears temporarily. If it returns, continue.
- Inspect flow switch wiring: Open the equipment bay and locate the flow switch on the heater tube. Verify the two small wires are intact, not pinched, and firmly connected to the Balboa or SpaNet control pack terminals.
- Check for misorientation: Ensure the arrow on the flow switch body matches the direction of water flow through the heater tube. If installed backwards, it can read closed incorrectly and must be reinstalled correctly.
- Test switch operation (basic): With power OFF, disconnect the flow switch plug from the control pack. Use a multimeter on continuity: with no flow (pumps off), the switch should be open (no continuity). If it reads closed all the time, the switch is stuck and should be replaced.
- Temporary diagnostic bypass (advanced, not for regular use): For testing only, a technician may simulate an open circuit at the control pack to confirm the board is reading correctly. Do not leave the spa operating with any safety switch bypassed.
If FLC persists after replacing the flow switch and verifying wiring, the control pack’s flow input circuit may be faulty and the entire control pack may need replacement by a qualified technician.