How to Wire Your Vehicle

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Cars are filled with stuff that can make or break performance. The engine needs to be fed the proper amounts of air, fuel, and spark. The suspension and brakes must be in tip-top shape. The wheels and tires, transmission, cooling system, gauges--even the seats--must all function properly.

With all those things to worry about, many enthusiasts overlook the electrical wiring system. A lousy wiring job will keep your electrical accessories from operating at full potential—and that means subpar performance.

Many guys are intimidated by the prospect of wiring a vehicle. But a proper wiring job doesn’t have to be a scary task—we’ve put together a few tips to help make the job a little bit smoother.

Gauge Your Wiring Needs
Once you’ve mapped out your wiring schematics, you can begin the actual wiring process. When you add electrical or electronic components to your vehicle, like high end audio or racing electronics, you need to use the proper wire. There are three factors to consider: size, material, and color.

Wire size  is measured by gauge—the smaller the gauge number, the larger the wire. The gauge you need depends on the current draw of the accessory and the wire length between the accessory and the power source. In general, the larger the current draw, the larger gauge wire you need to properly power the accessory. 

One factor to consider with long lengths of wire is voltage drop. The longer the wire, the greater the voltage drop. You can offset voltage drop by increasing the size of the wire. As a rule of thumb, try to maintain a less than .5% voltage drop to assure maximum performance.

Wire material is usually aluminum or copper. For automotive purposes, we recommend stranded copper wire for the greatest flexibility and conductivity.

Wire color may not seem important at first glance, but it becomes crucial when you try to trace a faulty circuit down the road. To keep yourself from tearing your hair out, color-code your wire by accessory. It will help you keep track of which wire goes where during installation and troubleshooting.

The Right Tools
The proper tools will make your wiring job a whole lot easier. The most obvious tools are a quality set of wire strippers. They will make quick work of just about any size wire, saving you valuable time in the process.

A good wire crimper is necessary when you install solderless connectors. Most quality crimpers have two or three sections on the nose to fit various lug sizes. You can even get crimpers with wire cutting and wire stripping sections.

A soldering iron is a must for splicing wires or securing oversized connectors that cannot be crimped. You will need solder designed specifically for electronics and wiring . It has a midly activated rosin core flux to clean the wire as it is being heated, removing oxidation and light corrosion. That allows you to solder with less heat, making the connections stronger with less electrical resistance.

Here are some other items that should be in your electrical toolbox:

• A wire brush for removing heavy corrosion, oil, or grease before soldering
• A volt/ohm meter to measure voltage and resistance levels in your circuits
• A test light to test for power within a circuit
• Shrink tubing to insulate connections from outside elements. The tubing slides over the connector or solder joint and permanently shrinks when heated
  

Vital Components
There is more to wiring a vehicle than, well, wire. For example, you will need some sort of overload protection to protect your expensive electronics. The three basic types of overload protection are fuses, fusible links, and circuit breakers:

Fuses are designed to blow when the circuits they protect are fed more power than the fuses are rated for. Fuses are rated by amperage; popular sizes are 3, 4, 5, 6, 7.5, 10, 12.5, 15, 20, 25, and 30 amp. Always use a fuse rated slightly higher than the accessory. For example, if an electric fan is rated at 19.5 amps, use a 25 amp fuse. 

Fusible links are another option. They are special wires made from an alloy with a lower melting point than regular copper wire. The link is spliced inline with an accessory’s power wire. In the event of an electrical overload the link will melt, preventing power from reaching the protected accessory.

A circuit breaker will switch off power to the protected accessory in an overload situation. When the overload has been corrected, the circuit breaker is reset. Circuit breakers come in manual reset and automatic reset versions, and in the same popular amperage ratings as fuses.

Relays are extremely useful for handling high amperage electrical accessories like large electric fans, fuel pumps, and HID headlights. Relays are activated by an electric coil and controlled by a switch. When the relay is closed, no power goes to the accessory in question. When you flip the accessory switch, an electric coil in the relay opens, sending power to the accessory. You can read all about relays in the fabulous "Relay Race" tech story.

There are plenty of other products to make your wiring tasks easier, including switch panels, multi-circuit main and auxiliary fuse blocks, toggle, pushbutton, and remote-mount switches, and ofr course,  wiring harnesses for everything from foglights and gauges to complete vehicles.