I’ve got a 1994 Z28 and I’m having an issue with the passenger power window. The window didn’t work then for a day or two it worked and then it didn’t again. I checked the fuses and the fuses are fine and when the window worked it wasn’t struggling or weak going up or down so I don’t believe it to be a window motor. I’m thinking it’s a ground but I don’t know where it would be.

 

Is there any difference, depending on whether you use the switch on the driver side or the switch on the passenger side?

If no one has changed it out, the power for the windows goes through a circuit breaker in the end of dash fuse panel. Someone may have replaced it if you found a fuse. There is also a thermal circuit breaker built into each window motor. If there's some binding in the track, increasing power draw, the internal breaker can trip. All the breakers should reset themselves.

Wiring schematic from Shoebox site:

http://shbox.com/1/pwr_window_schematic.jpg

The only ground is “G200”. Factory service manual indicates that is located “near base of LH A-pillar, bolted to instrument panel mounting stud, behind kick panel”.

 

No, there isn’t a difference between the switches neither work. I checked for power going to the window at the motor connection and there was power when the window wasn’t working but I didn’t check for ground so that led me to believe it to be a ground issue.

 

It is extremely common for the motors to overheat under normal use as they age. That engages the thermal protection circuit Fred mentioned.

The fix, if that’s what’s happening to you, is a new motor.

To help the new motor age more gracefully, I recommend a hotwire kit, which adds a relay and some heavier-gauge wiring to the setup. The idea here is that supplying the motors with less than their design voltage leads them to age more quickly. Some people say these don’t make a real difference, citing voltage readings being the same with and without the hotwire kit, but to my knowledge, none of those people did their tests while the circuit was under load (i.e. raising a window).

I got my hotwire kits with motors from AutoTrix. They also offer a version that adds an express-down function to the passenger side.

 

The circuit breakers in the motors will self reset a while after power is remove and they cool down. Either the motor is failing or the window tracks have gummed up after many years. In either case the fix will involve removal of the inside door panel.