Power Window Jam Protection Function


Window jam is detected by two components: the limit switch and the speed sensor in the power window motor.
The speed sensor changes the motor speed to a pulse signal. Jam is detected from the change in the pulse wavelength.
With the dead band of the ring gear, the limit switch distinguishes the change of the pulse signal wavelength in the case of jam and that in the case when the window is fully closed.
When the power window master switch receives the signal that notifies of a jam from the power window motor, it turns off the UP relay, turns on the DOWN relay for about one second and opens the window about 50 mm in order to prevent the window from closing further.
The jam protection function operation can be tested by inserting an object (such as a hammer handle) between the window and frame. When the window is almost shut, the jam protection function does not activate. Therefore, testing with hands may cause injury.
Some older models do not have the jam protection function.
The power window motor needs to be reset (to the initial position of the limit switch) in the following cases:
The window regulator and power window motor are disconnected.
The window regulator is activated when the windows are not mounted.
Any operation to change the window fully shut position is performed, for example in case of door glass run replacement.
(1)How to reset (in the case of Corolla (NZE12#))
Connect the power window motor and power window master switch to the wire harness of the vehicle.
Turn the ignition switch to the ON position and operate the power window master switch to run the power window motor idly in the UP direction for four seconds or more (between 6 and 10 cycles of revolution).

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