Having an auxiliary port with an AUX switch on your car's audio system allows you to connect an external audio device such as an MP3 player. The 2005 Ford F-250 truck includes an auxiliary port on audio systems equipped with the CD player. With an external audio device hooked up, you will be able to listen to that device's music through your F-250's stereo.
Connect one end of the 3.5 mm audio cable to the headphone jack on your external audio device.
Connect the other end of the 3.5 mm audio cable to the auxiliary port on the instrument panel.
Press the "AUX" button on the instrument panel to set the stereo to the AUX port. Audio from your external device will then be played through the car's stereo.
