Display shows FLC or FLOC; heater may shut down intermittently.

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

• Step 1 – Power cycle: Turn off power for 5 minutes, then restore. Observe if FLC appears immediately or only when pumps run.
• Step 2 – Inspect flow switch: Locate the flow switch on the heater plumbing. Check that the body is installed in the correct direction (arrow with flow). Look for signs of cracking or water intrusion.
• Step 3 – Check wiring: With power off, inspect the flow switch harness from the switch to the Nordic control pack. Look for pinched, rubbed, or melted insulation. Reseat the connector on the control board.
• Step 4 – Test switch function: Using a multimeter, test continuity across the switch with pump off (should be open) and pump on (should close). If it reads closed all the time, the switch is stuck or shorted.
• Step 5 – Replace flow switch: If the switch is stuck closed or shows water inside the housing, replace it with a Nordic-compatible flow switch. Ensure proper orientation and use Teflon tape on threaded connections.
• Step 6 – Suspect control board: If a known-good switch still reads closed to the board, the control pack input may be faulty and the board may need replacement by a technician.