The motor itself may be shot. There are two "gears" to a window motor, one that controls the up function, and one that controls the down. You can pull one from a junk yard for super cheap, and its an easy DIY. Best of luck!
The motor is probably shot as it has to work harder to push the window up because gravity assists when going down. Find the two leads going to the DC electrical motor and disconnect at the switch. Test the motor with a 2 volt battery. If the motor turns when connected, reverse the polarity at the connection point and the window motor should turn in the other direction. If he doesn't turn, with no load, it's shot.
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