HELP 1990 K5 tailgate wont open
 

My window goes up and down fine from the front switch, it goes up with the key at the back, but wont go down. My bigger issue however is the tailgate wont open. It seems to be locked. I will add that when the window is rolled down as far as it will go, there is still about 3/8 sticking above the window felt. Is that ALL the way down?? I removed the inspection panel on the tailgate, I cant pull the rods even to unlatch it. On the drivers side near the top by the latch is an electrical Piece with two heavy gauge wires going to it, is this a lock actuator? I cant seem to find it anywhere telling me what it is. Thank you in advance for the help!

Maybe there's something wrong with the internal electronic components? Check it out as soon as possible

I am sorry for missing this last year when you posted. I do hope that you got it figured out inspite of these seemingly spam posts that bumped it even if they brought it back to my attention.

As to your problem, if the window is not going down all the way, the latch mechanism will not function to drop the tailgate. 3/8" from being fully recessed is not all the way down. It sounds like you may have a few issues with the tailgate; window not fully retracting to enable the latch mechanism to drop the tailgate along with a malfunctioning window key switch in the tailgate. THIS THREAD has the wiring diagram for the tailgate electrical. THIS THREAD (on dieselplace) has some pretty good diagrams, pictures, & discussion that will likely aid you in your troubleshooting.

To start the troubleshooting, I would recommend getting someone to press the switch in the dash to lower the window while you push down on the glass itself. It may just be that the latch mechanism inside is stiff & not allowing the window motor to move things as required. If that doesn't work, you may have to remove the inner trim plate from inside the truck to get at things & get it to open.