Suburban tail gate not opening

[Cyrillious]

Hi, I am new to this and first time working on a carbureted vehicle let alone a truck Please excuse my ignorance to the technology I'm unfamiliar with. So I have a 1980 GMC Suburban k10 350 with a tailgate. What I understand is the glass needs to come down before the tailgate can be open. There is a switch which I tried to actuate while the engine was running but nothing happened. I thought the back where you put the key has a hand crank but I don't know how to operate it without breaking it unintentionally. Are the electric motors in the tailgate known to go bad and are there other common problems with this style of tailgates?

 

[Snoots]

If it's an electric tailgate there is no crank. Tailgate window motors can go bad at ANY time. Cheaper to rebuild than replace. You'll probably have to go in thru the inside (remove the tailgate panel).

 

[bucket]

The dash switch is hot with the ignition on. The key switch in the tailgate actually operates the window, it is hot at all times.

First thing to check is the harness connector, it's behind the rear bumper area. You may find that the connector is a big ball of corrosion or that it has already been cut out and bypassed in the past. If it passes a visual inspection, test for power on all three wires. One of them is 12v constant supply to the key switch (orange, iirc), one is power down from the the dash switch and the other is power up from the dash switch. If that all checks out, you will need to open up the tailgate from the inside panel and perform further diagnostics.

 

[Cyrillious]

If it's an electric tailgate there is no crank. Tailgate window motors can go bad at ANY time. Cheaper to rebuild than replace. You'll probably have to go in thru the inside (remove the tailgate panel).

I took a pic of the motor. Had a friend take it apart. Unfortunately didn't get pics of the inside but it was dirty. I got it back together and added 9vdc to motor out of frame but it wouldn't turn. The armature is trying to do something. Wondering if it needs to be grounded in frame for it to work proper.

 

[bucket]

I took a pic of the motor. Had a friend take it apart. Unfortunately didn't get pics of the inside but it was dirty. I got it back together and added 9vdc to motor out of frame but it wouldn't turn. The armature is trying to do something. Wondering if it needs to be grounded in frame for it to work proper.

The motor body is the ground. Apply 12v to one terminal to operate in one direction, then apply 12v to the other terminal to operate the other direction.

They don't operate like your typical car window motor of the last 30+ years.

 

[Snoots]

Like @bucket said. 9 volts ain't gonna cut it. You need at least 12.
You should have a heavy ground strap from the frame of the tailgate to the frame of the truck.

 

[Cyrillious]

When the weather gets better (probably a month from now) I will put the battery in and reinstall the motor and test it to see if the window goes up and down. I will update here when I do

 

[Cyrillious]

So an update on the unmovable tailgate window...

I installed the window motor. Turned the ignition to on, pushed the downside of the switch and it came down an inch and stopped. So I tried pushing the up part of the switch and got no upward movement. Tried down and came another 1/2 inch and got nothing after that... I have not thoroughly inspected the gears or the levers as this is very new for me. I will tackle this later. Any info to diagnose would be greatly appreciated.

 

[bucket]

Yep, start with what I suggested up there in post #3 I think it was. You need to determine if everything is getting power, and enough of it.

Did you try the key switch at all?