- 1). Identify the 12-volt power wires. You'll find up to three of these: a switched 12-volt power wire that supplies power when the ignition key is on; a dashboard power light that either powers a bulb in the radio face or triggers it to dim the display for "night" mode; and possibly an always-on 12-volt power source to maintain the time and pre-sets on your radio. The typical aftermarket radio will use a red wire for the switched source, a yellow one for the always-on battery and an orange one for the headlight switch.
- 2). Note the antenna and ground wires. The antenna wire is easy to locate, since older wires often use a screw-in, metal connector separate from the rest of the radio's wiring harness. Newer radios may use an antenna wire incorporated into the wiring harness. Cars with power-operated antennas will often incorporate the antenna turn-on trigger wire in with the amplifier turn-on. The ground is typically either a thick, black wire or a braided-steel tether attached to the radio.
- 3). Find the speaker wires, which are typically smaller in diameter than the rest of the wires, and are bundled together into groups of four or more. They come in colors that you wouldn't typically expect to see in an electrical system: You'll often find one speaker wire of a solid color pared with another with a black, white or colored stripe on it; the solid wire is generally the positive wire for that speaker while the striped wire is the negative one.
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