Strange rear window issue...

[SlicksInRain]

For about a year my rear window on my 90 didn't work at all. Recently I decided I had enough and opened up the tailgate to have a look. Looks like two wires connect to the electric motor. I played with them and now the window will only work one way... literally. If I switch the wires around it will only move down, if I switch them back it will only go up. The motor only responds to the switch inside the truck, the key in the tailgate does nothing at all.

I noticed a wire has been broken, the wire is by the tailgate on the drivers side and you can only see it when the tailgate is open. There seems to be around four wires and just one is split. I know this sounds like a stupid question, but is that the issue?

I thought the motor was shot, but it actually works when I flip the wires attached to the motor. Again if they are linked one way the motor will only bring the window down, if reversed it will only go up... no response in pushing the button the other way... it seems completely dead.

What to do besides fix that one wire? Again sorry if it seems dumb, but I am not sure what that "one" wire is for.

 

[496truck]

The wire on the driv side of the tailgate goes to a switch. The switch completes the circuit when the gate is closed. The switch is a common failure point. Should be 2 wires going to that switch, connect them together which will bypass the switch. Window should work from there. If not, dig further.

 

[Muddytazz]

What he said for bypassing the safety switch. Also on the key switch inside the tailgate. Tear into it and clean the copper contacts inside there. They get corroded over time due to the weather and stop working. Also when you have it torn apart, have a look and see if any of the contacts are broke. That is the case in my switch, one of the copper contacts is actually broke so it doesn't work. Haven't fixed it yet cause its not high on the priority list cause the inside switch works the window just fine.

 

[clandr1]

I had a similar issue with mine when I got it. Turns out I just needed to clean the contacts for the latch switch and it's working just fine now. Don't bypass the switch unless you're absolutely sure it isn't just dirty contacts. If the switch has failed, then go ahead and bypass the switch instead of spending money on a new one.

 

[SlicksInRain]

I had the switch bypassed years ago. I guess all I can do is repair the one ire and see what happens. Unless you guys have other ideas. Thanks.

 

[496truck]

Other thing I found, pull the wires out of the gate. Specifically, unplug them from under the gate, push them into the gate and pull them out through the big access door. You will see a couple factory splice connections, where 2 wires enter the gate and become 4, wrapped in tape. Pull the tape off and check those splices. If they are all green and crusty that is a voltage drop or bad connection. Repair it as needed and try it again.

 

[quinryan]

I had the same problem with mine (82 GMC w/ 6.2) and came up with a really workable and cheap (minded) solution.

The cable is just a speedometer cable. I just took a really long speedo cable out of a donor truck and used it to replace the "proper" cable at the motor. It's long enough to go to the back seat. Then, I keep a cordless screwdriver in the center console. It's a piece of cake hooking the screwdriver to the cable. You can probably figure out the rest.

While it's not as convenenient (at all) as having a working switch, it works really, really well and is a hell of a lot faster than the factory set up.

Yeah, I need to replace the switch and all, but this works for now.

 

[cdoggwsu]

I had the same problem with mine (82 GMC w/ 6.2) and came up with a really workable and cheap (minded) solution.

The cable is just a speedometer cable. I just took a really long speedo cable out of a donor truck and used it to replace the "proper" cable at the motor. It's long enough to go to the back seat. Then, I keep a cordless screwdriver in the center console. It's a piece of cake hooking the screwdriver to the cable. You can probably figure out the rest.

While it's not as convenenient (at all) as having a working switch, it works really, really well and is a hell of a lot faster than the factory set up.

Yeah, I need to replace the switch and all, but this works for now.

That is awesome.