The left rear power window in my 1990 brick read 245 goes down, but not back up without help. (I can get it back up with a palm on each side of the glass, pulling up while someone else works the button.

Do you think I have a weak motor? This has been a problem for a few months. I just removed the switch for awhile to keep it from going back down. Is a weak motor a probable cause for this problem or is it more likely the regulator or switches? Maybe the regulor is coming apart or weak. Is there a chance that the switches could be the culprit? I'll open it soon and find out, but I thought I would ask here first in case someone has experience with this.

I have read here that BOTH the master and the door swich have to work for the window to work. If they are corroded, could it cause this problem?

The regulator mechanism seems OK, the window moves smoothly, it seems to be a weak motor. If that is the case I hope it's interchangeable with the right side.

I have a spare window motor and switch from the right rear door if that might work, but I have not yet removed the door panel from the left rear door. (I just replaced the left rear door and hinges which were mangled when the door was left open and wrapped around the garage frame when the car was backed out. Was bad, but I managed to fix it with a $100 door from a pick and pull, same color, year, options. The left window I have been living with for awhile, but now that I have the extra motor from the right side door, I might use that on the left if it's the motor and it fits.

Any advice is appreciated. Thanks in advance.