What causes a window lift motor to suddenly stop working?

Common Causes of Sudden Window Lift Motor Failure

1. Abnormal Power Supply

A blown fuse or tripped circuit breaker prevents voltage from reaching the motor.

Loose wiring, corrosion, or broken connectors interrupt current or create high resistance.

2. Motor Failure

Burned windings or worn carbon brushes prevent the motor from generating torque upon receiving a signal.

Insufficient lubrication or worn bearings cause excessive rotational resistance, causing the motor to automatically enter protection mode and stop.

3. Mechanical Jamming

The window lift mechanism (guide rails, lead screw, connecting rod) is stuck or deformed, preventing the motor from turning even with power.

The anti-pinch device or limit switch malfunctions, cutting off power to the motor to prevent glass damage.

4. Control Unit Malfunction

Aging internal contacts or spring failure in the window switch prevent the signal from being correctly delivered to the motor.

A software or hardware malfunction in the Body Control Module (BCM) prevents the motor from receiving drive voltage.

How can I determine if the problem lies with the motor or the window switch?

1. Voltage and Current Testing

Use a multimeter to measure the voltage at the motor terminals while the switch is operating. If the voltage is normal but the motor doesn't turn, there may be an internal fault.

Simultaneously measure the current. If the current is abnormally low, the motor may be stuck internally or the coil may be damaged. If the current is normal but the motor doesn't turn, the control signal may not reach the motor.

2. Auditory and Tactile Judgment

If you hear a humming sound from the motor but it doesn't turn when the switch is operated, it's usually due to mechanical jamming or internal protection activation.

If there's no sound at all, and the power supply voltage is normal, it's more likely that the switch or wiring is failing to send a signal to the motor.

3. Bypass Test or Replacement Method

Temporarily connect a known working motor of the same model to the faulty door's wiring. If it can move up and down normally, the original motor is damaged.

Conversely, connect the faulty motor to a known working door's wiring. If it still doesn't work, there's a problem with the switch or the wiring.

4. Use a diagnostic tool to read fault codes

Modern vehicles' Body Control Module (BCM) records fault codes for the window lift system. Reading these codes can quickly pinpoint whether the problem lies with the motor, switch, or wiring.