Hand-drawn tailgate power window wiring diagram with two SPDT re…

The original wiring uses the dash switch and wiring to power the tailgate motor as well as ground the motor when using the tailgate/key switch, this causes high resistance for the motor as it has to go through several switches and travels a long distance on thin wire. This rewire provides a thicker wire to power the motor and a closer/better ground to allow stronger operation. It uses the dash switch only to power relays and requires the dash switch to use very little power to activate the relays. This will allow easy installation of additional switches for the tailgate as well.
The rewire uses the previous dash switch wiring and only requires 2 single pole double throw (SPDT) relays and an 8ga power wire going from your battery to the drivers side rear by the taillight. Once you have the power wire (red) going to the taillight, splice it to carry two wires going to the 87 post on each relay. Find the wiring coming out of the tailgate and cut 3 wires - 2 pink wires and the black/white wire. Connect the black/white wire (BK/W) to the 8ga power wire (this powers the key switch on the tailgate). One relay will only use the pink/light brown wire (PK/LB) and the other relay will only use the pink/light green wire (P/LG). Connect the PK/LB wire coming FROM the tailgate into the 30 post of one of the relays. On the SAME relay, connect the PK/LB wire coming FROM the dash switch into the 85 post. Do the same for the other relay only using the P/LG wire (FROM the tailgate going to post 30. FROM the dash switch going to post 85). Finally, ground the 87a and 86 posts to the chassis. Make sure to use a good ground, your tailgate motor will use this ground for power. To add more relays, simply splice into the P/LG and PK/LB wires, making sure your "UP" wire splices into the the P/LG and the "DOWN" wire splices into the PK/LB, this splice can be made at the dash switch or at the relay on the 85 posts.

Part of 1980-1986 Ford Bronco Wiring Diagrams

Owner caption December 2014 · Photo 2 of 27