2001 Chevrolet Suburban Electric window/sun roof

Tiny
UPMM019
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  • 2001 CHEVROLET SUBURBAN
  • 204,000 MILES
I purchased a used 2001 Chevrolet Suburban 1500 LT 4WD to be used as a hunting vehicle.

For the price of the vehicle I got some headaches, namely that the drivers side window does not work and the sun roof does not work.

Regarding the windows all other windows work but the drivers. I check fuses but had not luck finding the issues for either.

Hoping someone can give me some guidance as to how to best troubleshoot to determine the root issue so I can get both working again.
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Tuesday, October 8th, 2013 AT 11:40 PM

16 Replies

Tiny
CARADIODOC
  • EXPERT
If you can hear any noise from the driver's window motor, suspect the motor. The switch is more common though. There's usually a relay built into them that adds to the complexity. The easiest and fastest way to verify this is to find a good used one from a salvage yard and just plug it in to try it. Frayed and broken wires between the door hinges are somewhat common too, but then other windows would be dead while the driver's could work. Since the other windows work, wires aren't causing the problem.

Do you have a voltmeter or test light to test the sunroof motor? You should be able to make all the electrical tests right from the switch.
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Wednesday, October 9th, 2013 AT 1:49 AM
Tiny
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Yes I have both a volt and test light but need guidance on how to test.

I can try getting another module at a junk yard next week.

Also, I forgot to mention the electric mirrors do not work either so do you suspect in this case it would be the switch assembly?

You are right, no noise when the buttons are pushed. They are completely dead were the other three windows and other functions such as door locks work.
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Wednesday, October 9th, 2013 AT 4:38 AM
Tiny
CARADIODOC
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I prefer a test light for this type of work because it's faster when you don't have to turn your head to read the meter. Either way, if you already have the door panel off, go right to the two wires on the window motor. If you don't have the panel off, those two wires go into the switch, but I don't know the colors.

I also want a wiring diagram in front of me so I don't have to guess, but in the absence of that, troubleshooting is the same on any car or truck. One way to start is by measuring the continuity to ground from the two motor wires. Unplug the connector for that so a bad circuit doesn't read through the motor and the other circuit. Read each wire to ground with the ohm meter. If you don't know how to do that or how to read the meter, I can help with that when I get back to my computer later tonight.

Both motor wires should read near 0 ohms to ground. When you press the window switch one way, first it opens, (breaks) the circuit to ground for one wire, then applies 12 volts to that wire to run the motor one way. Pressing the switch the other way does the same thing, just to the other wire to run the motor the other way. There's actually four switch contacts involved in each window switch. GM often does that switching with a troublesome relay. Everyone else just uses switches with pretty tough contacts.

Another way to do the same tests is to measure the voltages at the window motor. This is best done with the motor plugged in. You should see 0 volts on both wires when the switch is at rest. Only one wire should get 12 volts when the switch is moved one way. When you move it the other way, the other wire will get 12 volts. If you find 12 volts on both motor wires at the same time, or 0 volts on both wires at the same time when the switch is pressed, you have a switch or wiring problem. I don't think you have a wiring problem because that would affect the other windows too.

These voltage tests can be done right at the switch too without removing the door panel to get to the motor. You don't even have to know the wire colors provided you can tell which two wires go to that motor. There's going to be a bunch of wires for the other windows to add to the confusion. You should find 12 volts on just one wire when the ignition switch is turned on. Next, activate the driver's switch and you should find 12 volts on a second wire, but only ONE second wire. 12 volts should not appear on two additional wires. If that test passes, move the switch the other way. Now 12 volts should appear on a different second wire. If that passes, it points to a defective motor, or there's a problem with the two wires going to it. There's no reason for the wires to break, but corroded connector terminals are always a possibility.
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Wednesday, October 9th, 2013 AT 1:22 PM
Tiny
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What is the quick and dirty to say it's the switch or the motor?
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Thursday, October 10th, 2013 AT 8:13 PM
Tiny
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Also, the mirrors don't work either and wondering about those and then the sun roof too.
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Thursday, October 10th, 2013 AT 8:14 PM
Tiny
CARADIODOC
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The only quick way to tell which is bad is to substitute the switch. That's easy to do with the passenger switches but not the driver's switch. I could jump the 12 volt wire at the switch to one of the motor wires to bypass part of the switch, but only if I had a wiring diagram to look at so I got the right wires. That has to be done while holding the switch applied in one direction. If the switch is released, both motor wires will be grounded, and jumping one with 12 volts will trip a circuit breaker or blow a fuse. For this type of switch failure, two totally different parts of it would have to fail for the window to not move in either direction. That isn't likely but this typically happens when the window is all the way up or down so you can't tell if it works one way. If you're lucky enough to catch it not going up, for example, but it's only half way down, if it goes down further, you know the motor is good. If it turns one way, it can run the other way. The only exception to that is on a lot of newer vehicles the window regulators are really cheap cable and pulley-driven affairs. If a plastic pulley breaks or the cable becomes frayed, the unit might run one way but get tangled and bind the other way.

I prefer taking voltage readings at the switch to diagnose a dead window. Once you have this diagnosed, the sunroof switch works the same way and you should be able to take the same voltage readings to diagnose it.
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Friday, October 11th, 2013 AT 12:21 AM
Tiny
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So, I checked the switch with the test light and got it to light pushing the questionable switch up and down.

In fact, if pushing up you can hear a little movement, not much. Nothing on the downside.

So I order a new motor but found an old new regulator and motor from a 97 grand prix.

I hooked it up and it does the same thing. I was expecting it to work.

Now I am stumped. Should I get a switch or is it something else?
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Friday, October 11th, 2013 AT 1:37 PM
Tiny
CARADIODOC
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I've been trying for a couple of hours to do something with the pdf files but I can't copy them or add notes. I'll just have to try to describe it. The engineers have really made the system unnecessarily complicated, but for some reason they left the driver's switch alone.

You should find 12 volts on the dark green wire. If that is missing, look for a broken or frayed wire between the driver's door hinges. I was incorrectly assuming that had to be good because the other windows are working, but I was working from memory of how all other manufacturers designed their circuits. GM had to be different. One of those "RAP" relays sends power to the other three windows, and the driver's lockout switch is in the ground side of the circuit, not the 12 volt feed side like normal. That means a broken wire will just affect the driver's switch.

If you have the 12 volts on the dark green wire, be sure it's still there when you press the switch. If that makes it disappear, there's still a broken wire but it has a carbon track in the insulation. A test light won't get enough current through that carbon track to light up so it will be more accurate in this case than a voltmeter.

Next, when you press the "up" switch, you should find 12 volts on the dark blue wire. If you do not, suspect the switch. At the same time you must not have 12 volts on the brown wire. If you do, suspect the switch.

Do the same tests in the "down" position. Now there should be 12 volts on the brown wire but not on the dark blue wire.
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Friday, October 11th, 2013 AT 2:35 PM
Tiny
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So I should do the following:

dark green - 12 volts. Nothing pressed

dark green - 12 volts - drivers window switch pressed

dark blue - 12 volts - up

brown - 12 volts - up

brown - 12 volts - dark blue - none - down
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Friday, October 11th, 2013 AT 2:42 PM
Tiny
CARADIODOC
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Those are the right voltages. You must have 12 volts on certain wires when the right switch is pressed and you must not have voltage when there shouldn't be any.
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Friday, October 11th, 2013 AT 2:49 PM
Tiny
UPMM019
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So this is what I did:

No Press, Green, 12 Volts - Yes
Press, Green, 12 Volts - Yes
No Press, Dark blue - No volts
Press, Dark Blue - 12 volts - Yes
No Press, Brown, No volts
Down, Brown, 12 Volts Yes
Down, Blue 12 volts Yes
Down, green 12 Volts Yes

Also, I hear a slight hum or squeal when I press up and you can hear the motor shift but you get none of that on the down.
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Friday, October 11th, 2013 AT 2:59 PM
Tiny
UPMM019
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Something is junk here.

I took a 12 battery and hooked it up to the window in the suburban and it worked, up and down.

So somewhere between the switch and motor there is something up.
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Friday, October 11th, 2013 AT 4:28 PM
Tiny
CARADIODOC
  • EXPERT
No Press, Green, 12 Volts - Yes (Good)
Press, Green, 12 Volts - Yes (Good)
No Press, Dark blue - No volts (Good)
Press, Dark Blue - 12 volts - Yes (Good, if you were pressing "up")
No Press, Brown, No volts (Good)
Down, Brown, 12 Volts Yes (Good)
Down, Blue 12 volts Yes OOOOPS!
Down, green 12 Volts Yes (Good)

The brown wire gets 12 volts switched onto it in the "down" position but the blue wire must remain grounded. You're showing it with 12 volts. That would be feeding through the motor. If you care to prove it to yourself, unplug the motor and that 12 volts on the blue wire will go away when "down" is pressed.

My guess is the window is all the way up already and at the end of its travel, so you can't tell that the "up" direction works. It's the "down" that is dead because of the switch. As another proof test, hold the switch "down" so that proper 12 volts is on the brown wire, then use a jumper wire to ground the blue wire at either end. If the window goes down, there's a burned or pitted contact in the switch. It is one that makes contact when the button is released.
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Friday, October 11th, 2013 AT 4:40 PM
Tiny
UPMM019
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So, I got frustrated.

Took the switch apart completely. Doused it with carb cleaner and iso alcohol and then air dried it with my compressor.

The switch now works, window goes up and down.

Hard to say how long it will last. Carb cleaner will probably kill it. Normally I have electric spray but couldn't find any.

So now. Moon roof. Where does one start?

I can post the wiring. But I can tell you when I push the button I hear nothing no hum, etc. I guess if it was used a lot could be the same thing where the switch is fouled out.
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Friday, October 11th, 2013 AT 5:45 PM
Tiny
UPMM019
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Here is the wiring for the sun roof.

http://www.knackjack.com/sunroof.pdf
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Friday, October 11th, 2013 AT 7:13 PM
Tiny
CARADIODOC
  • EXPERT
Here we go again. We've had motorized sunroofs for decades but now they don't work unless the insane engineers hang a computer module on it.

When you have a module like this and there's no way to know what goes on inside it, check the powers, grounds, and inputs. Assuming nothing is wrong on the output, if the powers, grounds, and inputs are there, suspect the module. To say it a different way, don't suspect the module until you've eliminated the other stuff.

With the ignition switch on, go right to the module and check for 12 volts on the red and dark green wires. Measure for continuity to ground on the black wire. If those are there, press the "open" button and check for 12 volts on the brown wire. Next, press the "close" button and check for 12 volts on the orange wire.

I'm gonna go out on a limb here and guess all of those wires are okay. Now check the output wires to the motor, black and red. When you press a button, one of those wires should get 12 volts, but only one. If both get 12 volts, you have the same bad ground problem that you just solved with the window, but this one will most likely be due to a bad contact on an internal relay, not the sunroof switch. Likewise, if you find 0 volts on both wires when a switch is pressed, suspect the module.

I recently repaired a $350.00 door module for a Corvette by replacing three ten-dollar relays. I would have cleaned the contacts with sandpaper but the relays were sealed. I think the GM engineers own stock in some relay company because they plant them everywhere including places they were never needed before. If you find the module to be defective, you have nothing to lose by taking it apart and looking for relays inside. If you find them, check the terminals for bad solder connections first, but they are turned on for such short periods of time, arced contacts are a better suspect.
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Saturday, October 12th, 2013 AT 2:51 AM

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