Car stereo hard wiring is necessary when wire harness adaptors are not available. Cut up original factory wiring harnesses will also require the car stereo to be hard wired. The process of hard wiring will involve soldering or connectors to connect the wires from the car stereo to the wiring of the vehicle. Soldering provides a more secure connection. However, store bought connectors will work for those without soldering experience. The wire connectors require a standard wire-crimping tool.
Obtain a wiring schematic for the vehicle's car stereo wiring. Find your specific vehicles stereo wiring diagram from online sources or from a store-bought general repair manual.
Disconnect the negative battery cable from the vehicles battery. This will ensure that electrical shorts will not occur while wiring the stereo to the car.
Use the wiring diagram for your vehicle to identify the continuous power, switched power, ground and speaker wires. Use the masking tape and fine tip marker to label all of vehicles car stereo wiring.
Use the wire-crimping tool to strip a 1/2 inch of insulation from the vehicle's stereo wiring. Gather the car stereo wiring harness and strip the ends of the wires in the same manner as the vehicles wiring.
Check the car stereo wiring diagram supplied with the unit. Mark the continuous power, stitched power, ground and speaker wires with masking tape and the fine tip marker if needed.
Twist together the corresponding vehicle wiring with the stereo unit wiring, starting with the switched power, continuous power and ground. If using bullet style connectors instead of soldering, crimp the connectors on to both vehicle wires and stereo unit wiring. Twist together the corresponding speaker connections of both vehicle wires and stereo unit wiring.
Double-check all of the wiring connections between the stereo unit and the vehicles wiring. Solder each connection and individually wrap each connection tightly with electrical tape. Skip this part if using crimped connections.
Plug-in the stereo harness connector to the back of the car stereo unit. Reconnect the negative battery cable of the vehicle to the battery.
Purchase stereo head unit mounting kits from a reputable source. Place a rag or piece of cardboard under the soldering area to avoid damage to the vehicles interior.
Use caution when using a hot soldering iron. Completely wrap any exposed bare wiring with electrical tape to avoid electrical shorts.