Control panel displays FLC (flow closed) even though water appears to be circulating; heater will not engage.

Safety first: Turn off power at the GFCI breaker before working in the equipment bay.

• Inspect flow switch: Locate the flow or pressure switch in the plumbing near the heater tube. Check for obvious cracks, leaks, or broken wires.
• Check wiring: Ensure the two-conductor cable from the flow switch to the main control board is firmly connected and not pinched or damaged.
• Test with power off: Disconnect the flow switch leads from the control board and use a multimeter to check continuity. With no flow, the switch should be open. If it reads closed (0 ohms), the switch is stuck or shorted.
• Verify orientation: Confirm the arrow on the flow switch body matches the direction of water flow. An incorrectly installed switch can cause false FLC errors.
• Replace if faulty: If the switch is stuck closed or shows continuity when disconnected, replace the Arctic Spas-compatible flow switch assembly.
• If problem persists: If a new switch does not clear FLC, the control board's flow input circuit may be defective and will require professional diagnosis.