Adding an auxiliary input to your Ford stereo will allow you to connect external sources to the vehicle's audio system. To play music and other content from your iPod or Mp3 device, you'd simply connect the device to the installed auxiliary adaptor. You would also be able to connect a satellite radio receiver or other media device without extensive adaptations to your stock radio, using the AUX input.
Remove the negative battery cable from the Ford's battery, using a Phillips head screwdriver to loosen the cable's clamp on the negative battery lead. Remove the lead from the negative lead post, until the installation is complete.
Insert the DIN removal tools into the holes on either side of the face of the stereo. Pull the tools outward to engage the mechanism for removal. Pull the tools with even force (left and right) until the stereo is removed from the dash.
Disconnect the wiring connected to the back of the stereo. The antenna and power supply to the stereo will be single cords that can be pulled from the stereo by hand. The speaker wires will be bundled in a white plastic wire binder. Pull the binder from the stereo.
Connect the wiring from the Ford to a wiring harness adaptor. (The adaptor will be clearly marked to show where the proper connections are to be made.) Connect the leads of the wiring harness to the Ford stereo. Connect the FM transmitter to the wiring harness adaptor.
Route the FM transmitter lead through to the inside of the glove box, next to the stereo mounting bracket. (The FM transmitter box can remain in the stereo's dock provided there is room for it to be stored behind the installed stereo deck. If there is not sufficient space, stow the transmitter in the glove box.)
Replace the stereo into the dash mount, by pushing the stereo unit into the mounting bracket until the clips on the side (that were disengaged by the DIN removal tools) are re-engaged and the radio is seated in the dash. Pull the DIN removal tools straight out of the face of the stereo.
Replace the negative battery cable onto the negative battery lead. Tighten the cable's clamp using the screwdriver.
You will be able to connect an external device to the FM transmitter jack located in the glove box. Aftermarket stereo units in the Ford may contain an established jack for an FM transmitter. If a jack is present, remove the stereo, connect the FM transmitter, and route the adaptor lead to the glove box. (There would be no need for a wiring harness adaptor in this case.)