Power Windows

billcar9999 · March 9, 2005

I need help finding the problem. My truck is a 2001 2500HD CC 4x4. When the window locks are turned off and I turn the key on (or start the truck), the left rear window rolls down. When the window is locked, the window will work correctly from the drivers door. All other windows work correctly when the window locks are on, meaning the individual windows won't work.

I've checked the wiring, swapped the drives door switch and had the dealer attempt to reflash the body control module. They said it had the latest flash and they couldn't find anything else obviously wrong with it. They didn't charge me either so that was a plus.

By the way, when I was at the dealer, the symptoms changed before they looked at the truck. I was able to reproduce some of the problems. When I left, the window actually worked like it was supposed to until I got about a block away from the dealer. Any ideas?

Thanks,

Bill

GM-Tech · March 9, 2005

When the window locks are turned off and I turn the key on (or start the truck), the left rear window rolls down.

Not that I have an answer, but can you clarify what exactly is happening? Are you saying when you turn the key on, the windows rolls down ... by itself?

billcar9999 · March 10, 2005

Yes, that is what happens except when the window lock is engaged.

GM-Tech · March 10, 2005

Yes, that is what happens except when the window lock is engaged.

The left rear switch AND the driver's left rear switch ultimately active the exact same relay by applying power to that relay. The lockout switch simply removes the power from all the window switches except the driver. So if the window works normally when the lockout is engaged, that tells me the "down" relay for that window is functioning normally and not stuck on.

With the lockout off, as soon as you turn the key on, power is supplied to the left rear switch, which if stuck in a down activated position, is activating the down relay, making the window go down. Again, the lockout simply removes that power source from that switch, preventing this from occuring.

Sounds to me like it almost has to be the left rear window switch unless there's some bizzare wiring problem that's feeding power from the dark blue wire from the lockout switch into the brown wire of the "down" side of the window motor somewhere within that door. The switch would be much more likely, but anything is possible.

GM-Tech · March 10, 2005

Here's the schematic if that helps you to understand what's going on. The lockout switch is not shown but it supplies power where you see the triangle with the "E" in it that's labeled "fuse block". That's near the bottom center of this schematic.

billcar9999 · March 10, 2005

I agree with your troubleshooting. It makes perfect sense. I'll let you know how it works out.

Thanks,

Bill

Wingnut · March 10, 2005

That's one of the strangest problems I've ever heard on this board. And would suck if it were raining fish and chips out.

GM-Tech · March 10, 2005

OOOPS! Guess I was half asleep last night. That circuit I was talking about is ground, not power. But the effect is the same if you just mentally think "ground" where I said "power".

billcar9999 · March 12, 2005

I knew what you meant. You were right. Good job. Looking at the switch I see where the board shorted. It looks like the circuit between m_dwn and +1 shorted and m_up got hot too. I'd bet the LED failed too. The LED may have been another clue.

I should have taken the switch apart when I had it out but I was gun shy from breaking the drivers door switch. The door switch was $44, drivers switch $77. All in all it was still cheaper than having the dealer work on it for several hours.

Thanks for your help.

Bill