Re: Tailgate replacement
In order to get the window down, remove the tailgate access pannel from inside the truck. Inside the tailgate, disconnect the rear-defroster connections and apply them to the window motor. Go to the front of the truck, and turn on the defroster to roll the window down! (if it doesn't work the first time, swap connections and - on the motor to reverse the direction.)
Now that the window is down, you can open the tailgate. Do the same procedure as above to raise the window half way. Unbolt the glass and slide it out. Now you are ready to find the problem. Check the connections into and out of the tailgate key switch. Also check all the tailgate wires. There is one that runs along the bottom of the tailgate, If you have rust, this one is highly likely to be corroded and should be replaced.
Important note: Power to the tailgate window is sent through the interior dash switch before it is sent to the rear key switch. This means if there is a problem with your inside dash switch, then neither switch will work. If you seem to be getting absolutly no power into the tailgate... Check this by removing the divers-side taillight, there should be a couple connetors there. One is the defroster, the other is a multi wire harness for the tailgate window. Disconnect it and probe all the pins for power, if you are absolutly reciving no power, then your problem probably lies within the interior dash switch.
I've taken appart my tailgate more times than I can count!.... I finnaly decided to replace all the wires inside the tailgate. The best of luck to you. Let me know if you need any further info on fixing the problem.