Yo!
Have you tested the motor directly from the battery using jumpers?
If not, do so... Unless you have done it & motor is shorted or open.
Where are you buying these motors?
Here is the wiring diagram:
Wiring Diagram in 87-96 (with under hood fuse box) (color codes are correct)
Source: by Seabronc
Testing by Ken:
"...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.
If it makes no noise, then it's probably in the electrical system.
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, 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 Seabronc's wiring diagram to trace it down, or tell us what you find.
A.2- 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 da wiring diagram to trace it down, or tell us what you find.
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 replacement Link above
C- If it doesn't run at all when wired directly to the battery, it sounds like it's time for a new motor.
Be aware that:
-The tailgate latch switch on the driver's side seems to be a common problem, check it early. Try pushing the driver's side of the tailgate in while holding the button or key switch in the up or down position.
-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.
-Ground for the motor is not connected to it's case, but supplied through the wires.
-There are seperate 2 power sources & 2 fuses 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..."
