Display shows FLC or FL2; heater is disabled and spa may run pumps but still reports a flow switch problem.

Safety: Disconnect power at the GFCI before working in the equipment bay.

• Step 1 – Reset: Turn off power for 5 minutes, then restore. Observe whether FLC appears immediately or only when pumps start.
• Step 2 – Inspect flow switch: Locate the flow/pressure switch on the heater plumbing. Check for cracked housing, mineral buildup, or kinked tubing (if pressure-style). Ensure the arrow on the switch body matches the direction of water flow.
• Step 3 – Check wiring: Verify the two-conductor cable from the flow switch to the Catalina control pack is intact and firmly plugged in. Look for corrosion on spade terminals or board connector.
• Step 4 – Functional test: With power off, disconnect the flow switch from the board. A technician can temporarily jumper the board terminals to see if the code changes, confirming a bad switch vs. board input. Do not leave the jumper installed—this defeats a safety device.
• Step 5 – Replace if needed: If the switch is stuck closed or open regardless of flow, replace the flow/pressure switch with a Catalina-compatible part.

If FLC persists with a new switch and good wiring, the control board input may be defective and the spa pack may need replacement.