How to Identify Am/Fm Car Radio Wires

By David Lipscomb

Wiring car stereos is easier when you follow wire coding.
i Thomas Northcut/Photodisc/Getty Images

Wiring a car stereo may initially seem overwhelming, given the numerous differently colored wires leading from the wire harness. However, these wires normally mean the same thing from one vehicle to the next, aided by the presence of aftermarket wire harness adapters. These adapters match the wire color-coding from vehicle to vehicle, providing virtually foolproof wiring after the meaning of each wire is ascertained.


Take a moment to examine the radio's harness. Aftermarket radio harnesses normally come detached from the unit, allowing easier connection to the harness adapter, sold separately. Wiring diagrams describing color and function are on labels stuck to the top of the head unit, offering quick reference. Lay out the radio's harness and the harness adapter, matching colors. The adapter's wiring scheme is detailed on the packaging as well as printed along the side of each wire. Getting acquainted with each wire in both harnesses before beginning the actual installation removes much of the stress and confusion surrounding the process.

General Wiring Codes

Wiring colors are pretty much universal from one harness to the next. Red and yellow wires provide constant and switched power, respectively. Black is the ground wire, while blue is accessory power. The latter is used to activate amplifiers, equalizers and other accessories that need to turn on with the radio. A blue wire with a white stripe is the power antenna lead. Gray, green, white and purple wires are usually front and rear speaker wires, respectively. The matching wires in these pairs featuring a black stripe are the negative leads. The orange lead is the illumination wire, coordinating the radio's display intensity with the rest of your dash lights. It is not uncommon to see harnesses with wires for features your vehicle does not have, along with holes left intentionally blank. Additionally, you may see an empty harness port on the factory radio, with no corresponding harness in the dash. This is because many car manufacturers use the same radio chassis with different internal features, depending on the way the stock systems are tiered.

Splicing Process

Crimping is the fastest and simplest way to join the wires between the two harnesses. To do this, pull off each pre-stripped insulation piece from the end of the wires. Twist the matching wires together to prevent frayed leads from sticking out of the crimp connectors and causing a short circuit. Insert each twisted wire pair into a crimp connector, also called a bell cap. Slide the elongated end of the connector into the jaws of a crimp tool and then squeeze the handles. Repeat this for each pairing. Neatly bundle the harnesses using a series of short plastic zip ties. Before you put everything back together, turn on the radio and check fade and balance to ensure all speakers are operational.


If you don't have any sound, check that the speaker wire colors are properly matched and securely crimped between the harnesses. If you have an outboard amplifier and have no sound, ensure the accessory lead labeled "ACC" is running from the harness to the amp's "REM" input. If you have an outboard amplifier that turns on when the radio is on and off when you put in a CD, you reversed the antenna and accessory wires at the harness. The antenna wire has a white stripe, while accessory is solid blue. If your radio constantly loses station presets or stays on after you exit the vehicle, double-check that the constant and switched power wires are matched correctly.