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I have a 90 Bronco, 5.0, and am having either motor issues or wiring issues for the driver's side window and the tailgate window. Besides this, I also do not have back-up lights. I am wondering if the tailgate window and light problems may be related and if anyone can give me an idea of a place I should be looking to test if I find it's not the window motor. I'd like to make this a one day project, so any heads up I can get would be great. Thanks.

Driving Stuff Henry Built
-90 xlt, 351w, e4od, man 1356, 3.55, sag, warn hubs, 35s. -73, 400, np435, d20j twin, 35s
8,078 Posts
Below is a pic of the fuse layout on my 90. It shows the backup lights on fuse #5, & the tailgate motor on #12 & 14 (One is for the dash switch, the other for the tailgate switch). Since they're on separate circuits, I'd guess the issues to be unrelated. The motor itself usually isn't the problem with the back window. There's some testing to help pinpoint it. I'll throw in my usual response, with links to more info & pics, at the bottom of this post. The info on torque pins applies to the front windows too.

Click for a larger image.

Tailgate Window

The stuff below is mostly cut & paste from an earlier reply, but it covers a lot of tailgate window stuff. Use what applies to your situation.

Be aware that:

-The tailgate latch switch on the driver's side seems to be a common problem, check it early. It keeps the window from being moved when the tailgate is open, & if not latched right, it'll keep the window from working at all. Try pushing the driver's side of the tailgate in while holding the button or key switch in the up or down position. If that makes it work, check out Steve83's "How to align a Bronco Tailgate" link in #5 below & JKossarides info on door striker bushings in link #6 below.

-Ground for the motor connects up front, & at rest runs from there through both switches & both wires to the motor.

-When either switch is operated, 1 side's ground is disconnected & replaced by hot at that switch.

-Ground for the motor is not connected to it's case, but supplied through the wires.

-There are 2 seperate power sources & 2 fuses/circuit breakers for positive. 1 for each switch.

-The same 2 wires are used throughout for both up & down (Polarity is reversed by the switches).

-When the tailgate is open, you have to close the driver's side latch for the window to operate. Remember to open it before closing the tailgate.

Some good resource links:

1-Fireguy50's wiring diagram, see post 2. Great color diagram, it makes it much easier to understand what's going on.

2-Steve83's Tailgate Tech. Great pics & info. Look through the entire section for the portion that applies to your problem.

3-adrianspeeder's pics (He's doing torque pins for a passenger window, for the tailgate you don't need to drill).

4-Torque pins, motors, etc.

5-Steve83's How to align a Bronco Tailgate

6-new bronco owner from hawaii Post 3 has JKossarides' info in replacement striker bushing numbers & wiring harness issues.

7-Fireguy50's Re-wire your Tailgate window switch (FINISHED) Upgrade diagram using relays.


Does it make any noise at all? Like the motor's turning, but the window doesn't move? If so, there are torque pins in the motor's drive gear that commonly break & aren't too bad to replace. See the torque pin, Steve83's Tailgate Tech, & Adrianspeeder's links above. If it makes no noise, then it's probably in the electrical system. Fireguy50's wiring diagram is linked above.

To test the electrical system, remove the access panel from inside the tailgate. Run test wires from the battery directly to the window motor connector (Yellow & red wires coming right out of the motor) to confirm that the motor works. To lower the window, it should be positive to red, & negative to yellow. Be ready for the window to move, keep hands & wires clear. Make all the connections but 1, then connect & disconnect the last wire quickly to see if it tries to go the right way. If it tries to go the wrong way, reverse the wires (This also makes it so that you can lower the window & get the tailgate open to continue testing).

A- If it runs & the window moves when wired directly to the battery, perform the following tests:

A.1- With both switches at rest & the latch switch closed, connect a tester between the positive test wire from the battery & each wire from the tailgate loom at the connector for the motor. Both should read 12v. If they do the ground is good. If they don't, refer to Fireguy50's wiring diagram linked above to trace it down, or tell us what you find.

A.2- With the latch switch closed, connect the tester between the negative test wire from the battery & each wire from the loom at the connector for the motor. The red wire should read 12v when either switch is in the down position, the yellow wire should read 12v when either switch is in the up position. If they don't, refer to Fireguy50's wiring diagram linked above to trace it down, or tell us what you find.

A.3- If everything tests ok, but it still doesn't run, there's a couple more possible causes to check:
-Sometimes the connector for the tailgate motor will test ok, but not make contact when plugged in. You might try backprobing the motor side wires with the plug connected. On mine I removed it & soldered the connections.
-It's possible for a damaged wire to carry enough load to show 12v on a tester, but not enough to operate the motor. Look for worn areas, especially in the loom between the body & the tailgate.

B- If it runs but doesn't move when wired directly to the battery, in addition to your electrical problem, the torque pins in the drive gear are probably broken too. Run the electrical tests in section "A" above, & see the torque pin, Steve83's Tailgate Tech, & Adrianspeeder's links above for the torque pin replacement.

C- If it doesn't run at all when wired directly to the battery, it sounds like it's time for a new motor. See Steve83's Tailgate Tech link above & use the info for removing & replacing the motor.

On my truck there were multiple bad connections, so it was hard to isolate the problem. Someone before me used a ton of crimp connectors :doh0715:. Basically I ended up removing them & soldering all the connections, & eliminating the corroded plug to the motor.

710 Posts
as per your backup lights... Could be a few things, a corroded plug inside the tailight housing, a bad wire, or a messed up reverse light switch... Seems like we have lots of issues with bad grounds in these trucks, but then again they are getting pretty old now.

Also don't ever give up on just a bad bulb... sometimes they can look perfect, but still be bad.
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