So, I'll skip the usual "what's wrong with my tailgate" question that will most certainly end up in a "search the forums" answer. It's a 1988 and what I want to know is, how do I go about figuring out where the problem is? The key in the tailgate doesn't work, neither does the switch. A fuse didn't do anything either.

What should i do next? I'm a weekend warrior who just wants to know what I have to do (within reason) to figure out the trouble. I assume it's going to be an electrical answer, but I'm at a loss when it comes to that kind of thing. Anyone know where to start and how?

 

I have the same problem with my 94! I also have a 95 in perfect condition.
I still haven't done this (lazy) but this is a good start for us both.

Back-up a good bronco to the bad bronco, almost bumper to bumper so that the driver sides are aligned.

Connect the tailgate wiring harness (located by the rear bumpter - driver side) to the bad.

Use the switch or key of the good bronco to lower the window of the bad.

If nothing happens, then your tailgate window motor is bad.
How do you replace it? Well, you'd have to remove the covers from the inside and replace the motor.

-Stranger

 

Yeah, the replacement thing I'll worry about later, it's the original diagnosis I want to figure out how to do now. The Bronco idea would work, but I'm limited by having only one Bronco and probably no way to get another nearby to actually try the harness thing.

 

Keep in mind that there are TWO power feeds for the tailgate window motor... one for each switch. The auto-restting circuit breakers in positions 12 and 14 in the dashboard fuse block BOTH feed the tailgate window. CB #12 feeds the keyswitch and CB #14 feeds the dash switch.

If it won't work from either the dash switch or the T/G switch, make certain that the gate is shut tight. The driver's side latch has an interlock switch that will prevent the window from moving if its not fully engaged. Older latches and striker posts will tend to let the latch close but not latch fully. If you are suspicious that this is the problem and feel the need to bypass the interlock switch you can by removing the inspection cover from the inside of the gate and pulling the TAN/BLACK and RED/YELLOW wires from the switch (mounted on the back of the driver's side latch) and jumping them together.

If that still doesn't get the window moving, listen. If the motor can be heard running inside but there is no movement its time to replace the Delrin pins that secure the drive gear to the motor. The Graveyard sells a gear/pin kit for about $6-8.

If there is no sound from the motor, check the internal tailgate wiring harness, the harness section between the gate and the jamb, and finally, UNDER the rear bumper near the driver's corner there is a connector, check it as well.

Last resort, jump power from the battery to the YELLOW/RED wire and ground the RED/YELLOW wire. This SHOULD run the motor and send the window DOWN. If not try swapping the polarity.

If NONE of this works you are in for the tedious and finger-jamming experience of removing the regulator arms from the window channel from inside the truck with the gate closed. As if that wasn't enough fun, you have to be prepared to "catch" the window when you release it from the regulator or it may fall suddenly and slam into the bottom of the gate rendering the glass slightly less than usable. Once the window is free from the regulator you can remove the regulator with the motor attached. You can then get on to the process of replacing a dead motor.

If you can let the glass all the way down you can get the gate open and work on the inside of the gate with it open rather than closed. You will then have to manually slide the window back up to get to the regulator and motor. Take the necessary precautions when leaving the glass "up" with the tailgate open. (i.e. some sort of support or whatever).

 

This is another reason why I asked. I never 'jumped' anything. I'm almost 100% sure that the tailgate is secured as that was the first thing I checked when I first noticed this. Neither of the two--key or t.g.--makes a sound motor-wise.

So, what do you mean by jump, and is this something someone with no real electrical experience can play with? She's not my daily driver now, but it would be nice to get the rear window working again before it gets nice out.

 

Good write up greystreak92. I think this would be a good subject for a "sticky".

The only thing I would do different is to first take the inspection cover off and run wires from your battery to the inside back of the bronco. I would unhook the power going to the motor and put the wires you ran directly to the motor. One way will move the window up and the other will move it down. I did it and put a fuse in between. If the motor runs then move the window down and open the tailgate and look at the driver side latch on the body. My latch had the plastic sleeve broken and did not engage the catch in the tailgate and the sensor did not realize that the tailgate was closed. You can trick the sensor by manually closing the latch with your hand and then trying the key or dash switch (connect motor back up first).

Important: make sure you open the latch back up before you close the tailgate. I had a lot of trouble opening the tailgate back up because one side latched and the other did not.

1988 EB Bronco - 302 - AOD - 3.55 Lim Slip 8.8- Manual Hubs and Transfer Case - BFG 32/11.5 AT - 209,000 miles

 

When you disconnect the two wires from the interlock switch, use a short length of wire or some metal device (paperclip) to connect the two ends of the wires that had originally been connected to the switch. This will effectively bypass the interlock switch. Make certain they are securely touching metal-to-metal as you are making an electrical connection.