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Properly Wiring Aftermarket Head-Unit

Model Years: Any Make/Model Estimated Time: 0:30
In this edition, you will be guided through the basic process of wiring your head unit and creating a sturdy harness that won't fall apart over time. Too many times have I re-installed head units in peoples cars, only to find that the Best Buy or Circuit City employee used electrical tape or even CUT the factory plugs completely off and hard-wired it! Even I used to wire my stuff with electrical tape, which simply will not last. Using Wiring nuts is good, but for better long lasting connections, use butt connectors. (I didn't use them b/c I transfer my head units between different makes of cars which uses different factory harnesses).

The pictures illustrate me wiring a New Pioneer 740MP Head unit to a 1990-1994 Mazda Protege wiring harness (bought for about $18 at Circuit City). I also installed a "Super Turbo" installation kit made by Metra. I bought that for $15 from Pep Boys.

Tools you will need:

  • Proper Harness for your vehicle ($18 is going rate for them, from Pep Boys, Best Buy, Circuit City, etc.)
  • Wire Stripper / Cutting / Crimping Tool(or penknife will work good too)
  • 6-12 small Zip-ties ($1.29 pack of 30 at Home Depot or Lowes)
  • 12-16 blue Wiring nuts ($3.69 box of 100 at Home Depot or Lowes) OR 12-16 blue butt connectors (probably a better choice)


Installation Instructions:
  1: Unpack Harness from new head unit, and Unpack harness for your particular vehicle.
2: Using your wire cutters, Trim the factory harness to about 3-4" total legnth for each wire. Trim the head-unit harness to about 3-5" total legnth. You might want to trim the blue remote lead wire and black ground wire only just a little bit, leaving both at about 8" total legnth, since you will not wire those into the factory harness. After trimming, use the stripper to strip about .5" off of each wire end, to expose the wire threads.
3: Get both harnesses and spread the wires out so you can easily see which needs to be wired to what. Also, if you won't be using certain wires, use your zip ties to tie them up out of the way (or you can just cap them off with a wiring nut). In this picture, I tied up the orange illumination wire since my head unit has a built in illumination adjustment. I also tied up the yellow/black wire which was some kind of cell-phone attenuator function (not all head units will have this). The blue wire on the factory harness doesn't need to be used, and since i'm not using the illumination wire, I also tied that up with it.

4: Use the blue wiring nuts and twist them onto the color coded wires. There should be two purple (one positive one negative), white, grey and green wires (one for each speaker) a yellow (constant power), red (ignition power), black (ground), blue (remote wire, used for remote turn on wires in external amplifiers), orange (dash illumination switch).

After Wiring these together, use the zip ties to tie the speaker wires apart from the rest of the wires. Zip tie both harness's wires together to make it nice and sturdy, but don't zip tie them too much, you still want the harness to be long enough to easily plug into the factory plugs in your car
5: Another angle of the harness you created
6: take the harness, and plug it into your factory plugs. It should clip right in. Take the ground wire and a blue wire nut and wire the ground wire to your car's ground lead. If you have an amplifier, wire the blue remote turn-on wire from your amplifier to the blue remote wire from the head unit harness. Plug in the attenna banana connector into your head unit, any RCA wires from your external amplifiers.
  7: Get your car keys and turn it into the "On" position. try to work the head unit, it should function properly. If it doesnt, check all of your connections
  8: Follow the instructions with your head unit installation kit, and install the head unit into it. Then install the entire kit/head unit into your dashboard.
9: The finished result!!
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