DIY Car Wiring Tips

01
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DIY Car Wiring Starts With the Right Tools

DIY wiring tips
You'll need many of the same tools for a DIY car wiring job that you'd need for any other wiring or electronics project, including wire strippers. Jetta Productions / Blend Images / Getty

Before you start any DIY electronics installation project in your car, it’s vital to make sure that you’ve put the right tools and materials together. Whether you're installing a head unit or any other electronic device, the main tools that you're going to need are:

  • wire strippers
  • soldering iron or crimping tool
  • digital multimeter (or a test light in a pinch)

In addition to those tools, you’ll also need some materials to complete your DIY wiring project:

  • solder or butt connectors
  • proper gauge wire
  • electrical tape or heat shrink

02
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Check the Circuits

fluke dmm
A Fluke DMM is an essential part of technician or serious enthusiast's toolbox, but any old digital multimeter will get the job one. Image courtesy of Hiroshi Ishii, via Flickr (Creative Commons 2.0)

If you have a wiring diagram, you can use it to help find the wires that you need to connect your new equipment to. However, it’s still a good idea to use a digital multimeter (DMM) to check that you have the right wires. With a DMM, you can check the circuit polarity and verify that the proper voltage is present.

A test light will also do the trick in a pinch, but test are a little different from digital multimeters. Since test lights use incandescent bulbs to indicate the presence of voltage, they put a load on the circuit. That’s not a big deal in most cases, but if you have a DMM it’s better to be safe than sorry.

03
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Disconnect the Battery

disconnect battery
Disconnecting the battery can save you a headache in the long run. Image courtesy of Dave Schott, via Flickr (Creative Commons 2.0)

One of the most vital tips for any DIY car electronics wiring project is to disconnect the battery before you get started. The only time the battery should be connected is when you’re testing wires to verify that they have power or ground, or when you’re testing your new equipment before you button everything up. Leaving the battery connected while you’re wiring in new electronics can result in damage to either the new device or other equipment in your car, so it’s a good idea to just pull the negative battery cable.

If your wiring project doesn’t involve replacing the factory radio, make sure that the existing head unit doesn’t have anti-theft protection that kicks in whenever the battery is disconnected. If it does, you’ll need to know a special code to get the radio working again. The code or reset procedure is sometimes located in the manual, but the service department at your local dealer may be able to help if it isn't.

04
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Use a Wire Stripper

wire stripper
A self-adjusting wire stripper makes this job a breeze, but regular wire strippers work fine as well. Image courtesy of Andrew Fogg, via Flickr (Creative Commons 2.0)

Wires can be stripped with any sharp object, but the easiest, cleanest way to get the job done is a wire stripper. Scissors, razor blades, and other sharp objects can do the trick in a pinch, but you run the risk of accidentally cutting all the way through the wire or generally making a mess of things. With a wire stripper, you can take off the proper amount of insulation every time.

05
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Don’t Use Wire Nuts

wire nuts and butt connectors
Wire nuts (foreground) are bad news for wiring car electronics; butt connectors (background) get the job done. Image courtesy of flattop341, via Flickr (Creative Commons 2.0)

Wire nuts are fine for electrical wiring in your house, but you don’t blow down the freeway at 70mph in your house, or take it down bumpy back roads. Due to the constant vibration that’s generated whenever you drive your car or truck, even the tightest wire nuts will tend to loosen up over time. In a best case scenario, that will just cause your device to stop working. In a worst case scenario, something might short out.

06
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Use Solder or Butt Connectors

solder
Solder and butt connectors are both fine for DIY car wiring projects, but solder has the edge. Image courtesy of Windell Oskay, via Flickr (Creative Commons 2.0)

The best way to complete any DIY wiring project in your car is with a soldering iron and electrical grade solder. If you know how to solder, and you have the equipment, there’s no better way to get the job done. A good solder joint will stand up to the daily vibration in your car, and it will also protect the wires from oxidation.

If you don’t know how to solder, butt connectors are another solid option. These connectors look like little plastic tubes with metal sleeves inside. You use them by stripping the wires you want to connect, sliding the wires into the butt connector, and then squeezing it with a crimping tool. This is the easiest way to wire any new electronics in your car or truck, but you will need a crimping tool to do it right.

07
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Insulate Your Wire Connections

insulate DIY wiring
Heat shrink is the best way to insulate your wires, but electrical tape will do in a pinch. WLADIMIR BULGAR / Science Photo Library / Getty

The last, and possibly most important, DIY wiring tip is to properly insulate your connections. Whether you use solder or butt connectors, proper insulation will help make sure that your wiring job doesn’t fall apart, corrode, or short out in a few years.

Heat shrink is the best way to insulate wiring connections, but you have to remember to cut the tubing and slide it over the wires before you connect them. You can then slide it over the connection and heat it up until it creates a tight seal around the wires. Some soldering irons have special tips that are designed to activate heat shrink tubing, but simply placing the tip of a hot soldering iron near the tubing will often do the trick (just be careful not to melt the heatshrink by actually touching it with the soldering iron).

Electrical tape will also get the job done, but you have to make sure to use a high quality product. If you use low quality electrical tape, or other sorts of tape, it may peel off, crack, or otherwise come apart over time.