Over the past 10 years there have been so many new developments on car stereo systems and with this, new techniques to installing head units. There are some opinions of what is right and wrong when wiring up a system, the fact a technique works, does not necessarily means that it’s correct.

The Majestic Modifications Opinion

Being an expert opinion, they recommend first, if applicable, always use the harnesses. The aftermarket wiring harness will usually take the guesswork out of the installation. These harnesses attach to the vehicle’s factory wiring harness and give you a color coded installation. You just attach red to red, yellow to yellow, etc. But is that all an installer should know? What if you don’t have the wiring harness? Just follow the below guidelines.

Using a multimeter, find the power sources in the harness. One source will be continuous 12 volts, the other will be the ACC (ignition) 12 volts. These two will go with the yellow and red wires from the aftermarket head unit’s harness. They are labeled accordingly. It is usually a good idea to attach the ground wire to the frame of the dash. Most of head units come with a connector for this already attached to the ground wire. Be sure you have a good ground wire connection.

Secure these in place with some solder and shrink tubing. Slip the shrink tubing over one of the wires to be connected and move it out of the way. Connect the wires and dab a little solder on the wires. Let cool and then slide the heat shrink tubing over the connection. Heat with a heat gun/hair dryer to shrink the tubing to fit.

About The Wiring Colors…

As there exist “typical” wire colors, chances are you will find different ones. You can try two techniques to find the right wires. Clip the rest of the wires from the factory harness. You can test the speakers with a good 9 volt battery to see which speakers are which. Two wires connected to the same speaker will make it pop. Note which speaker makes the pop and attach it to that speakers wiring from the head unit. You can turn the unit on and make sure the wires are the right polarity. A reverse wired speaker will not have as good a sound as a properly wired one. Continue the technique until all the speakers are connected.

Another way you can trace the speakers down is to turn on the head unit, but be VERY careful not to cross any wires. Start with a pair of wires, and attach them one at a time until you get sound. Note which speaker it is and attach it to that speaker’s wires from the wiring harness, taking note of polarity. Continue until all the wires are in place. Zip tie the wire together and neatly tuck them behind the head unit.

Be sure that RCAs or signal wires are running away from any power wires or sources, and are not run parallel to them.

A Neat Trick

You can attach the 12 volt acc to the illumination wire, and you will be able to turn the unit on with your parking light switch. Take note, that anytime the unit is on, the dash panel lights will be on too, but you won’t notice them in the daytime. The illumination wire is used to turn the factory radio lights on at night.

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