E19 displayed and the unit reports a problem with the bypass valve position sensor.

Safety: Unplug the unit before accessing the bypass sensor or wiring.

Steps:

• Verify handle position: Ensure the AquaClean bypass handle is fully in the "Service" or "Bypass" detent, not between positions.
• Inspect sensor: Locate the bypass position sensor or microswitch. Check for physical damage or misalignment with the bypass mechanism.
• Check wiring: Confirm the sensor harness is connected securely to the control board and not pinched.
• Test switch: Use a multimeter to test continuity of the sensor in each bypass position.

Replace the AquaClean bypass position sensor if it fails continuity tests or is physically damaged.