Display shows ERR2 and regeneration stops mid-cycle on US Water Systems softener

Safety: Disconnect power and close the inlet valve. Open a faucet to relieve pressure before removing the valve cover.

• Locate the position sensor: On most US Water Systems electronic valves (Matrixx/Flexx), a micro-switch or optical encoder is mounted near the main cam/gear. Inspect for loose mounting screws or misalignment.
• Check wiring: Ensure the sensor harness is firmly plugged into the control board and not pinched or damaged. Repair or replace any damaged wiring.
• Test the switch/encoder: With a multimeter, check continuity on a mechanical micro-switch while manually rotating the cam through its positions. For optical encoders, verify that the encoder wheel is intact and not cracked or missing segments.
• Clean and reseat: If the sensor is dirty (iron, dust, salt), gently clean with a dry cloth or compressed air. Reseat the sensor so it properly engages the cam or encoder wheel.
• Replace if defective: If the switch/encoder does not change state when the cam moves, replace the position switch/encoder assembly with a US Water Systems compatible part.
• Reprogram and test: Restore power, clear the error (if applicable), and initiate a manual regeneration. Confirm the valve moves through all cycles without stopping and ERR2 does not reappear.