عملگر شیر خراب

The actuator that moves a control valve, failed so the valve is never driven — as distinct from a valve that is jammed. The module cannot tell them apart: it commands a position, does not see it reached, and reports the valve.

Establishing which half has failed is the whole diagnosis and it is a physical test. Disconnect the actuator and move the valve by hand: a valve that moves freely means the actuator is at fault, and one that is stiff or seized means the actuator was working against something it could not overcome. Doing this before ordering anything is the difference between one repair and two.

Vacuum actuators fail as a torn diaphragm or a leaking supply, and hold-test with a hand pump; electric ones fail as an open winding or a stripped gear, and the winding's resistance at the connector distinguishes those. A gear that has stripped will often still hum when commanded, which is a useful sound: power is arriving and nothing is moving.