Could anybody enlighten me on why a power window motor stops when the window reaches either the fully open or fully closed position; I know that there are no limit switches.

 

The motors/regulators themselves have the limit switches.

 

What kind of switches are they and how do they function?

 

in reality what happens is the relay kicks off because of the load when the window reaches full up or down.

 

Is the relay located inside the window motor?

 

Depends what vehicle. Some are all controlled through computer modules. Relays are often located in the relay panel in the engine compartment.

What seems to be your problem?

Greg, if the window sense resistance, it should go back down, no?

 

Thank you guys for interest in my question. I took the window motor out of a door of my 1990 Crown Victoria to rebuild the gear part, and I was just curious how the motor knows when to stop, since the power to the up/down switch comes directly from a breaker in the fuse panel.

 

it will not go down on most cars because it does not reverse the ground,on the cars that does have the safety feature it is controlled probably by the GEM or body module

 

I just checked the power on the window motor when you push the up/down switch; the power stays on even when the window stops (with the switch still pushed), which means that some kind of load sensor inside the motor cuts off the power to the motor windings.

 

did you check the ground side of the circuit to see if it was interupted?

 

I checked it and it was not interrupted, so the puzzle still remains...

 

I will take the window motor apart and look inside.

 

Call me crazy, but mine allows you to stop in the middle...LOL

 

I would think that all electric windows would allow you to open them halfway if you elect to, e.g. you remove your finger from the OPEN/CLOSE button when you want it to stop moving. My initial question pertains to the case when you push the OPEN/CLOSE button and hold it until the window is all the way up or down, and the window stops moving even though you still push the button.

 

I know on every car I've ever owned with power windows, the "thing" that makes the motor stop when the window reaches the limits of its operation is just that....the motor stalls when it can't move the window any more. But the motor is still receiving power. The automakers assume you will let your finger off the button as soon as the window is where you want it. I can tell that the motor is still energized on my car even when the window is fully open or shut if I'm still holding the button down, because the interior lights will dim until I release the window button. Similarily, if the window is already "up" and I push the "up" button anyway, nothing will happen, but you can see the dash lights dim due to the load going through the stalled motor.

 

beach boy is correct, after I looked at several wiring diagrams for several different cars I did not see where the power or ground was being turned off or interupted what happens is the motor reaches a load limit and stops just like your portable power screwdriver when you hold the chuck to tighten a bit, it just stops. I hope this answers your question.

 

Thank you all for your interesting comments, I am sure that we now have found the answer and that the window motor just stalls when it hits an obstruction of any kind.