Safety first: Disconnect power and place the softener in bypass before opening the control head.

Locate home switch: On Nobel control valves, a small micro‑switch or sensor is used to detect the service (home) position of the cam. Identify this switch and its actuator tab on the cam.
Check alignment: Manually rotate the cam (with power off) to the service position indicated in the service manual. Ensure the actuator properly engages the switch. Adjust the switch mounting if necessary.
Test switch continuity: Using a multimeter (if qualified), check that the switch opens and closes as the cam moves past it. Replace the switch if it does not change state.
Inspect wiring: Verify that the switch wires are intact and firmly connected to the control board.
Reset and test: Restore power and allow the unit to perform its homing sequence. If it finds home without error, run a manual regeneration to confirm proper operation.

If E17 persists, the cam or motor assembly may be damaged and the entire control valve head may need replacement.

E17 error and the unit cannot detect the home position after power‑up

Possible Causes