Models: K, Years: ALL

If you have a 710K, here's how to easily change the wiring so that the joint lamps and the rear dome lamp turn on when you open any of the three rear doors.

Features of the modifications:
1. Costs less than $10 (or maybe nothing).
2. Easy to do and easy to reverse.
3. Allows switching between original mode and new (civilian) mode.
4. Allows turning on joint/dome lamps from the front cab.

How to do it:
WARNING - disconnect battery power before doing any electrical work on your truck !!!

First of all, if all you want is to be able to turn on the joint lamps/dome light when any of the three rear doors are opened, then simply remove the blue wire(s) from terminal 87 on the relay (see photo below). Then remove the red wire(s) from terminal 87a and put them on terminal 87. Be sure to tape up the end of the blue wire. Pull out the light switch at the relay and you're all set. The blue light will no longer function and the joint lamps and rear dome lamp will turn on whenever any of the three rear doors are opened (the switch at the relay must be pulled out and left in that position).

If, like me, you want a civilian style light function as described above, but want to retain the original military function (to impress your friends and neighbors, or whatever), then you will need a DPDT switch. I chose a center off type switch so that I could actually select either mode or disable the rear lighting altogether (same as turning off the switch at the rear lighting relay). I also wanted to be able to turn on the rear lights from the front cab, so I added another switch which I will describe later. I chose to mount both switches on the radio table. In the photo below, the toggle switch controls the function and the red rocker switch is the remote turn on.

Cut four #18 wires (five wires if you want a remote turn on switch for the rear lights) long enough to reach from the interior lighting relay to where you intend to mount the switch box. Either use different colors for each wire or mark the wires. Crimp a female disconnect terminal on two of the wires and a male disconnect terminal on two more wires, all at the relay end. Disconnect the blue wire(s) from terminal 87 on the relay and connect the wires to one of your male terminated wires. Connect one of your female terminated wires to terminal 87 on the relay. Then disconnect the red wire(s) from terminal 87a on the relay (terminal 87a is just behing terminal 87 on the photo) and connect the wires to the other of your male terminated wires. Connect the final female terminated wire to terminal 87a on the relay.

Here's the wiring diagram of the toggle switch:

Finally, If you want a remote switch for the rear lighting, the fifth wire is connected to terminal 86 on the relay (the black wire) along with the other connections (to the door switches). I used a crimp-on tap connector. The other end of this wire is connected to a SPST switch, and the other terminal of this switch is connected to the chassis ground.

Testing and Operation:
After the wiring is complete, put the DPDT switch into the center (off) position, reconnect the battery, then pull out the switch at the relay and leave it in the out position. Hopefully you will not see copious amounts of smoke and sparks Shocked. If so, immediately disconnect the battery, put out the flames, and check your wiring . If you have managed to keep the smoke inside the wires (where it belongs), then you can proceed to flip the DPDT switch to one side. If all three rear doors are closed (and the remote switch is off) then you may or may not see the the joint lamps/rear dome lamp come on. Open any rear door. If the joint lamps/rear dome lamp come on, then the switch is in the "civilian" position. [Note: both the joint lamps and the rear dome lamp have separate switches. Make sure all these switches are turned on for this test.] If the blue light comes on when any of the doors are opened, the the new switch is in the "military" position.

Finally, check your (optional) switch for remotely turning on the rear lights. The switch should have tha same function as the door switches, so if the DPDT switch is in the "civilian" position, then the joint lamps/rear dome lamp should come on.

Contributed by Jay Reich