I have a 1995 bmw 525i and the driver side window won't go down. I ran electric current directly to the window motor and it works. The regulator and motor both work fine. What else could it be? What are the common causes of this problem if it isn't the motor or regulator?

i bet the wire that goes through your drivers side door is broken. open the door take off the protective covering and see if the wires are broke. if they are just reconnect them, tape tightly with electrical tape and put the cover back on.

Common is the switch is gummed up with spilled beverages. And people wondered why BMW was among the last car maker to add cup holders..

I have seen the little mirco switch that tells the computer the window is already up mess up and cause a fault.

Did you check to see if the wires were good thru the door. Take out the drivers bottom (floor) speaker and unplug the big harness and check for continuity. I've never seen this problem BMW has a pretty good system for the body to door wire jump..

The switch is probably bad. By switch I mean the button you press to tell the window to go up and down. Probably need to replace that and you will be good. BMW parts are expensive so you may consider used.