August 2011 Randy’s Electrical Corner - Jp Magazine

If you are cheap or broke like me you find creative ways to get things done. Now, “creative” can often mean “hack job” so many of my more “creative” things I don’t show you guys. However, when Trasborg started complaining about not being able to see anything in his Comanche at night, I was able to figure out how to fix it with stuff I had laying around. Unlike the pile of transformers I have (no, not the Optimus Prime kind—the kind you pull out of dead TVs) and the drawer full of capacitors I have kept for years “just in case,” the parts I used for this one are commonly available; I will even run down the part numbers for you if you want to do this at home.

august 2011 Randys Electrical Corner randy Photo 37099740

The problem is that every Jeep I’ve seen uses a negative-switched interior light, and every cheap light I’ve seen is setup to have a constant ground and interrupt the positive. This makes the two things as far from wanting to work together as possible. The other problem is that the cheapy lights are only setup to be either on or off with a manual switch. If you have doors on your Jeep who wants to manually switch the interior light on and off? Isn’t the whole reason to have doors so that when you open them the interior lights come on?

august 2011 Randys Electrical Corner wiring Diagram Photo 37099752 Similar to every other Jeep I’ve messed with, this one uses a constant positive to the interior light bulb and the door switch interrupts ground. Here’s the way I wired it up.

So by using a cheap light, an old relay, and a single-pole double-throw center-off switch I was able to give Trasborg a much better interior light that has all the functions that a stock light has. It can come on with the doors, can be turned on manually, and has an “off” position too.

PhotosView Slideshow I wasn’t sure how I was going to get it done, but I knew I wasn’t spending money on this project so I fished through the stuff I had on hand and found this light (Napa PN LIT 549SWD); the problem was that it had a pushbutton switch and one side of it would go to ground once the light was mounted. The wire was riveted to the metal plate that was going to get screwed to the metal of the truck. I tried a few different ways to get it to work with the stock lights, but it just wouldn’t. I wanted it to work like a dome light should: on with the doors, on with the switch, or off. So I knew I needed a different switch, one with two positions and a center off. I found this little switch on the shelf (Radio Shack PN 275-325) and with a couple of washers I made it fit the hole that was already in the dome light lens. Then the only problem I had was how to make the light come on when I wanted using the wires running to the factory interior lights—in other words, without running new wires and new fuses back to the fuse block. The solution was easier than I thought. By using a regular relay (Napa PN ECH AR143 or Radio Shack PN 275-001), I was able to change the ground interrupt of the factory system over to a positive interrupt that would work with my grounded light housing.