There are really only a few surprises in life--most things are predictable. One example is electrical problems with your 4x4. If the truck is 20 years old (and so is the wiring) and you've hacked into it a few times for upgrades, repairs, or last minute add-ons, there should be no shock when a portion of the system fails or when the whole thing goes up in smoke. We know you don't want either of these situations to happen, so here's what you can do about it.
Assess the Situation
Look at what you’re starting with. Arranging chairs on a sinking ship is ridiculous, so take a realistic inventory of the condition of your 4x4’s wiring. You may be able to save time and money and avoid frustration by ditching the entire factory system and starting over. In most cases, however, you’ll only need to better organize what you have, combine several power leads into a couple of fused lines, and perhaps add a secondary fuse box.
Tools of the Trade
To do electrical work, you really only need two tools: a test light and common multipurpose electrical pliers. If you’re starting your electrical toolbox from scratch, buy a kit from your favorite auto-parts store that comes with pliers, connectors, a test light, and a plastic box to carry it all in. These are convenient on the trail so you can help others that didn’t read this article. Connectors come in a few varieties. The most common are solderless, crimp types, and they work fine for most applications. There are also solder-types that, when soldered and insulated with shrink tubing, make permanent connections with very low resistance. Painless Wiring offers crimp-type connectors with shrink tubing that form a watertight seal.
Wire comes in different sizes and of varying quality. Size is measured in gauge: The smaller the gauge, the larger the copper core is. Higher amp loads require larger wire (10-12 gauge) to operate without overheating the wires. Smaller loads, such as taillights and CBs, work fine with 14- to 16-gauge wire. Quality is a function of the copper strands used in the wire and the insulation. Fine strands of copper are generally higher quality than coarse. Insulation has two aspects important in a vehicle. The first is the heat resistance--does it melt at 110 degrees F or 300 degrees F? The other consideration is resistance to abrasion. A soft insulation is easily cut away, exposing the copper wire.
Cut or frayed wires, connections made by twisting and taping wires together, and inadequate wire are the most common forms of butchery that can be fixed easily. Now that you have tools and supplies, repairing damaged parts of your 4x4’s wiring is as simple as finding the problems and replacing the bad parts. Frayed wires should be replaced. Often you can simply splice in a new section of wire, but it is sometimes necessary to replace the whole wire. Several wires cut in the same place is a bad situation. In this case, stagger the splices so you do not have a massive bundle of butt connectors in the same place. This builds excessive heat.
Connections made without terminals are also easy to fix: Just install the proper connector. If you find household speaker wire anywhere on your vehicle, replace it with the correct wire. Even for your 4x4's speakers, automotive speaker wire has better insulation than household stuff, so use the right wire. If 16-gauge wire supplies your death-ray off-road driving lights, replace it with heavier-gauge wire and consider installing a relay to lessen the chance of electrical disaster.
More Power Scotty
Perhaps the biggest problem with off-road vehicles is that the factory electrical system is overtaxed when you add aftermarket gauges, a stereo system, a CB, off-road driving lights, and other electrical accessories. The fuse box isn’t designed to handle half a dozen more gadgets. This is when wiring gets ugly. You normally add these one at a time, and things don’t appear to be a problem until you’ve spliced into a power source under the dash for the fourth time.
If you're only adding one item, go ahead and tap into the fuse box. If you know that eventually you want to add everything we mentioned before and who knows what else, then add another fuse box just for accessories. Many off-road electrical add-ons connect directly to the battery, so you should also consider a junction block close to the battery to supply power and ground connections.
Painless Wiring offers auxiliary fuse boxes in several sizes; two are even waterproof so they can be mounted outside the cab. These supply both keyed and full-time 12-volt power sources so you can run a variety of accessories.
For junction blocks, the one we like best is the Connection from M.A.D., which has plastic shielding to keep objects away from the metal portions. Supply power to the Connection with a heavy-gauge wire (either 4- or 6-gauge) and mount it close the battery to keep this main power-supply cable short. You can use the same thing for a common ground near the battery.
Wrapping it Up
Just as most things are predictable, avoiding bad situations is relatively easy. Look at what’s in place, fix problems before you have a meltdown, and install new equipment correctly.
Armed with this how-to, search your vehicle for potential electrical problems and map a trouble-free future of adding electrical equipment.