Do Your Own Car Wiring Installation

Avoid shortages and malfunctions when wiring your car's electronics

This article provides a few tips for wiring your car stereo yourself.

What You'll Need Before You Begin

Depending on the complexity of the job, you're likely to need:

  • Wire strippers
  • Soldering iron or crimping tool
  • Digital multimeter (or a test light in a pinch)
  • Solder or butt connectors
  • Properly sized gauge wire
  • Electrical tape or heat shrink

Check the Circuits

Use a wiring diagram (if you have one) to find the wires to connect your new equipment. Use a digital multimeter (DMM) to check that you have the right wires, check the circuit polarity, and verify the proper voltage.

Fluke DMM being unboxed

Hiroshi Ishii / Creative Commons 2.0 / Flickr

A test light will also do the trick in a pinch, but test​s are a little different from DMMs. Because 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.

Disconnect the Battery

Always disconnect the car battery. Leaving the battery connected while you're wiring in new electronics can damage the new device or other equipment in your car, so just pull the negative battery cable. The only times the battery should be connected are when you're testing wires to verify that they have power or ground, and when you're testing your new equipment before you button everything up.

Disconnecting the battery of a car

Dave Schott / Creative Commons 2.0 / Flickr

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 a special code to get the radio working again. The code or reset procedure is sometimes in the manual, but the service department at your dealer can help if it isn't.

Use a Wire Stripper

Always use a wire stripper to strip wires. If you use scissors, a razor blade, or another sharp object, you might accidentally cut all the way through the wire or generally make a mess of things. With a wire stripper, you can take off the proper amount of insulation every time.

Self-adjusting wire stripper on tile floor

Andrew Fogg / Creative Commons 2.0 / Flickr

Don't Use Wire Nuts

Wire nuts are fine for the electrical wiring in your house, but you don't speed down the freeway at 70 mph in your house or take it down bumpy back roads. The vibration a vehicle generates on the road can loosen even the tightest wire nuts over time. In a best-case scenario, that will simply cause your device to stop working. In a ​worst-case scenario, something might short out.

Wire nuts and butt connectors in a pile

flattop341 / Creative Commons 2.0 / Flickr

Use Solder or Butt Connectors

The best way to complete any DIY wiring project in your car is with a soldering iron and electrical-grade solder. A good solder joint will stand up to routine vibration and protect wires from oxidation.

Wire solder in a spool
Windell Oskay / Flickr / Creative Commons 2.0

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. Strip the wires you want to connect, slide the wires into the butt connector, and then squeeze it with a crimping tool. This is the easiest way to wire any new electronics, but you need a crimping tool to do it properly.

Insulate Your Wire Connections

The last, and possibly most important, DIY wiring tip is to insulate your connections. Whether you use solder or butt connectors, proper insulation will help ensure 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 must remember to cut the tubing and slide it over the wires before connecting 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.

Be careful not to melt the heat shrink by touching it with the soldering iron.

Electrical tape works, too, but you must use a high-quality product. If you use low-quality electrical tape or the wrong kind, it can peel off, crack, or wither over time.

Spool of heat shrink it insulate wired connections
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