Adding an auxiliary input to a vehicle's stereo sound system enables you to connect external devices such as iPods, satellite radio receivers, and DVD players. Connect such devices by way of an "AUX in" line. If you wish to connect an auxiliary input to your factory-installed car stereo units, and are handy with tools and equipment, consider doing it yourself. Otherwise, it might be wise to hire an audio technician that specialises in car stereos.
Lift the bonnet and disconnect the negative battery cable from the negative battery terminal. Rest the cable away from the battery. Move inside the vehicle.
Remove the vehicle's stereo. Consult the vehicle's repair manual for instructions. Disconnect the stereo wiring and antenna cable from the back of the unit. Plug the stereo wiring in the wiring harness adaptor leads. Plug the wiring harness's adaptor lead connectors in the outlets on the back of the stereo.
Plug the signal and power connectors from the FM modulator in the leads of the wiring harness adaptor. See the adaptor manual for correct connection locations. Plug the antenna cable lead in the FM modulator's antenna input. Plug the antenna lead from the FM modulator int the FM antenna outlet on the back of the stereo.
Stow the FM modulator main box in the rear of the stereo dock. Feed the FM modulator input cable lead into the adjacent glove compartment.
Replace the stereo in the vehicle's stereo mounting dock. Consult the repair manual for installation instructions for your specific vehicle.
To use the AUX input, tune the stereo to the frequency printed on the FM modulator. Plug the external device (satellite radio receiver, MP3 player, etc.) Adjust the volume for your speakers.