We're starting today with with a niche electronics question!
Issues in my passenger side window (1996 base LT4) and after testing it I found it was the switch, which only delivered power in the up direction (the problem I had with the window coincidentally). After poking and prodding with a multimeter, I believe the issue is that the small mylar capacitor (it looks like a red square with two wires) died after 30ish years.

Now, here's the question: all the capacitor sits between us the "down" ground pin and the actual ground wire. What issues would you see with soldering the up and down grounds together and bypassing the capacitor?

Notes: I actually did this and it still doesn't work, in either direction. Switch does now deliver voltage in both directions though. So maybe it's now the motor? I hope not. Also, when plugged in, somewhere on the switch starts to generate heat under load, not sure what.

What do you guys think? I hope I just made a stupid wiring mistake and need to replace the capacitor, but I'm no electrician. I did however attach the FSM wiring diagram for y'all's convenience.



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It has been eons since i read schematics, so i wont try to answer your specific question but I have a troubleshooting question back to you.
you say the issue is with your passenger side window. does the same thing happen when you use the driver's side switch as it does w the passenger side one?

 

Yup, it does. An electrical engineering friend of mine took a look at the passenger side switch and said it was the capacitor, but we're students so we could be wrong.

 

Sounds like a noise suppressor, did you try it without the capacitor, without tying them together ??
Did you try measuring a known good capacitor so you can replace it. The capacitor may be 30 years old but the physics haven't changed. A capacitor of that value is available, maybe a different package but still functional.
One part of your discription does not add up, ""all the capacitor sits between us (is) the "down" ground pin and the actual ground wire. What issues would you see with soldering the up and down grounds together and bypassing the capacitor?""
If they are both true grounds they are already tied together, but are they ?? There is only 1 motor, in order to reverse that motor the polarity must be swapped, it can't be tied to ground permanently, right ?? I find the C4 corvette infamous for their engineering designs for reversing motor direction, truly these were the hippy years !!! I am surprised the relays and switches weren't painted psychedelic colors !!!

 

So, you guys think best thing to do would be test driver side switch for power in both directions?

 

Yes. Check the driver's side and trouble shoot the power there first.

 

Ok, a few problems here.
As stated above the capacitors are needed. Both to control arcing in the switches and to protect the driver side motor control PCB.
The capacitors are not connected between two grounds. They go to bi-directional control lines.
switches are shown on schematics in there “normal” state. In this case the normal with nobody touching the switch state is both lines are connected to power. For the passenger window these would be the Lt Blue and tan wires.
If you move the switch to UP the Lt. Blue wire is grounded and power runs from the tan wire through the motor to ground. If you move the switch to Down the tan wire becomes ground and power is connected to the Lt Blue wire and runs through the motor in the opposite direction. Once the window hits a stop in either the up or down direction the current increases and triggers the PTC to stop the motor. PTC’s act like a circuit breaker. They have a low resistance until a set current is reached then they go to a high resistance state and the motor stops. They won’t reset until power is removed. Which is what happens if the switch is release back to the normal state.
if the drivers side window works then that portion of the switch is OK. No need to fix it.
go to the passenger side switch and disconnect it. With ignition on accessory put a volt meter between the Lt blue wire and ground at the passenger socket. There should be 12ish volts. Now to tan and ground. Should be 12v again. Move the DRIVERS side passenger switch switch to up. The passengers side socket should have 0v on Lt blue, 12v on tan. Move to down should have 12v on Lt blue and 0v on tan. If works like this the passenger switch is probably bad. If it doesn’t the driver side switch is probably bad. If in any position you see a voltage between 12v and 0 v that also counts as bad since the PTC won’t reset and the motor won’t turn.
with the passenger side switch disconnected you can also test the window motor buy applying power to the dark blue and brown wires. One to power, one to ground. Flip to change direction.

 

Thanks for the insightful post. Very helpful.

my comments weren’t directed at you. I was writing my “wall of text” when you posted your reply. They crossed.
I suggest in the future you just ignore me and I will ignore you.

 

Oh, one additional thing I discovered today. When I plug in the passenger side switch, the one with the capacitor delete, activating the switch in either direction dims the lights and lessens the AC. Not sure if this happened before or not, I just now noticed.

 

Did as you said with the tan and blue wires, it gives a pulsing +/- 4 volts in either direction. Back when I had the door apart, this was the same thing that I measured at the motor. Think this could be the problem?

 

Yeah sorry, should have described it better don't have a ton of experience with electrical things.

With red lead connected to Tan and black lead connected to Blue off a multimeter, with the car in accessory, I read +/- 4 volts when pressing the switch for the passenger side window on the drivers side door.

 

Since the capacitor blocks DC, I don't think it's the problem.

 

Unless it is 30 years old, and shorted…