Q: How Does the Anti-Pinch Feature Work on My Power Windows?

Basically, anti-pinch works by measuring the amount of electrical current the motor uses that drives the glass up and down. Like practically everything on a modern car, the windows are controlled by an electronic control unit (ECU). When you operate the switch for the window to go up or down, you’re actually just sending a signal to the ECU that you want the window to go up or down, so the ECU energizes the motor and the window goes up or down. During the trip, the window motor will draw current within a certain range, which the ECU keeps track of. If the glass runs into an obstruction on the way up, the load on the motor goes up and it draws more than the normal current. The ECU senses this and says “Hey! Something’s blocking the glass!” and applies reverse voltage to lower the window a few inches.

So how does the ECU know when the glass reaches the top of its travel normally? It has to be trained. This is why after the battery is disconnected and you use the auto-up feature, the window goes to the top and drops; it has lost its memory and defaults to anti-pinch mode. To retrain it, pull the window switch up and hold it for five seconds after it reaches the top. Repeat for all the power windows in the car. If you need to have your window switch inspected, don’t hesitate to call a professional technician, such as one from YourMechanic.

Safety note: even though the car has anti-pinch on the windows, there may be enough pressure from the glass to cause bruising or other injury before the glass drops, so be sure hands, arms, legs, etc. are clear of the opening when closing the window.