How to test and send power to passenger side window switch?

[Ben_Olddermin]

I'm trying to fix my slow passenger side window in my 87 truck. It's slow going up and down, and it needs a person to help it go up. I have already replaced the window motor and the regulator with new AC Delco stuff. So we can rule that out.

I need to test and see if it's a poor voltage problem, or a drag on the window itself. Or both. Does anybody know what each colored wire does, for the passenger window switch? Then I'd know exactly where to send power with the Power Probe. That would tell me the answer. If the window is fast when supplied with power directly, I don't have a frictional drag.

I searched and found this for an 87.  Anyway I'm not so good at reading electrical schematics. Looks like the passenger side switch is at the very bottom right, but I'm not certain where to plug in the volt meter prongs to test the voltage. Or where to send power. Thank you



Power Windows
 

[bd]

Pink is B+ feed to both door switches.  But be careful when applying power to circuit components.  The 1982 - 1987 model power windows function by reversing the voltage polarity supplied to the window motors.  By default, all motor wires ground through the door switch controls when the switches are at rest (not deflected).  Only when a window control is flipped "UP" or "DOWN" does one of the motor wires change from ground to power to complete the motor circuit, causing glass movement.

Take voltage measurements only while the motors are actually powered and running.  Static measurements while the motors are at rest are uninformative and can be very misleading.

[bd]

Before chasing electrical causes, make absolutely certain that the window channels are properly adjusted and all window mechanisms are liberally lubricated since mechanical issues are the fundamental cause of sluggish window operation.  The glass should move up and down freely and not be pinched by its channels.  Once all mechanical causes are eliminated and power supply validated, consider retrofitting relays into the window wiring.  Scroll to the bottom of the thread linked in your initial post.

[Ben_Olddermin]

Yeah I would just detach the window from the motor. And see if it drags on anything. Is there an easy way to do that? When I installed the motor and regulator, it was all one piece at the time. Not sure how to detach them while they're inside the door.

I was hoping for some easy verification before I started tearing into it and spending more money. The Power Probe can do that if I am able to use it correctly.

It looks like I need to supply power to the brown wire and then the dark blue wire. The pink wire should be the main power feed to the plug. Then from there electricity goes to either the blue wire, or the brown wire. Depending on if you press up, or down. Does this sound about right?

[bd]

It looks like I need to supply power to the brown wire and then the dark blue wire. The pink wire should be the main power feed to the plug. Then from there electricity goes to either the blue wire, or the brown wire. Depending on if you press up, or down. Does this sound about right?

Unfortunately, you have to separate the glass along with its attached lower sash from the regulator.  It's not an easy task, but necessary to verify the glass isn't binding in the channels.

You have the basic electrical concept, but be wary of applying power if bypassing the switch while the switch is connected to the circuit.  The switch grounds both motor wires constantly while the switch is in its rest position.  When the switch is thrown in either direction, it disconnects one of the motor wires from ground and reconnects that wire to power; the switch simply reverses polarity across the motor to control its direction of rotation.  If you bypass the switch while applying power, and the switch is still connected to the motor, you will be "shocked" at the 4th of July display!

I think you would be better served by making voltage drop measurements with everything connected as designed from the factory to determine whether voltage is being wasted across connections, wire, switches, etc.  Just remember to make the measurements while the system is operating and not static.

[Ben_Olddermin]

It looks like I need to supply power to the brown wire and then the dark blue wire. The pink wire should be the main power feed to the plug. Then from there electricity goes to either the blue wire, or the brown wire. Depending on if you press up, or down. Does this sound about right?

Unfortunately, you have to separate the glass along with its attached lower sash from the regulator.  It's not an easy task, but necessary to verify the glass isn't binding in the channels.

I think you would be better served by making voltage drop measurements with everything connected as designed from the factory to determine whether voltage is being wasted across connections, wire, switches, etc.  Just remember to make the measurements while the system is operating and not static.

So no way out of rebuilding the door. IIRC the vent window has to come out in order to get the main window glass out. It also means that I'll probably have to replace the felts that run down inside the door.

When it comes to voltage drop measurements, let me see if I follow you: I need to find out what the maximum vdrop that GM allowed for from the factory. Do you happen to know how low the voltage should drop on each wire when the switch is pressed? My guess is not below 11v.

It sounds like I need to test the voltage (during operation) on 3 wires. Brown, blue, and pink. Any of those 3 could be the problem.

[bd]

The lower end of the rear channel has to be unbolted from the door so it can swing out of the way but the vent window assembly remains firmly bolted in place.  Unless the channel felts are worn out, you shouldn't need to replace them.  It has been long enough, now, that I don't recall with certainty whether the regulator/motor assembly has to be unbolted from the inner door panel to separate it from the glass.  You may be able to detach the glass by running the regulator arms to an optimum height and sliding the glass laterally with the rear channel unbolted.  Hopefully, another will chime in to clarify the procedure. 

In a perfect world, 100% of the battery voltage would be delivered to the window motors with no loss across the wiring.  Alas, that is never the case.  Nonetheless, the vast majority of the voltage (>90% or ~12.8+ volts with a fully charged battery and the engine running) should drop across the window motor while it is energized and raising the glass. 

Measure the voltage across the battery with the engine running to establish a power source baseline.  The charging voltage should measure 14.2 - 14.5 volts.  Then with an assistant raising the window, measure the voltage inside the cab at strategic points (e.g., both terminals of the 30-amp circuit breaker, both power window switches, and the right window motor).  Ideally, the cumulative voltage loss across the wiring components with window operating should be within 10% of the system voltage measured at the battery.  If <90% of the system voltage at the battery is measured across the motor, additional voltage drop tests can be performed to precisely narrow down and identify the cause(s).

And, don't neglect the cab ground.  Measure the voltage between the negative battery terminal and a spot of bare cab sheet metal while an assistant operates the window with the blower set to high speed.  That should be ample electrical load to validate the cabin sheet metal ground at <0.3-volt difference with respect to the battery negative terminal.

[Ben_Olddermin]

Thank you for the replies. I have the electrics all figured out now. Also the glass is out and so is the vent window. I removed the felts and there does appear to be some bare rubber exposed here and there. I suppose it's possible the glass could be catching on the exposed part where there is no felt.

I will install a new felt window run track and see if that fixes the juddering. It also seems to catch and shake on the way down, so that makes me think it could be the worn felts. There's not a whole lot of felt missing, but there are a few small 1-inch places here and there.