Understanding your Audi A4’s radio wiring diagram is crucial for a successful aftermarket stereo installation. This guide provides a step-by-step walkthrough, accompanied by images, to help you navigate the process. We’ll cover everything from disconnecting the battery to finalizing the installation and ensuring all components function correctly.
Disconnecting the Battery and Accessing the Radio
Before starting any car audio work, always disconnect the negative battery terminal. This prevents accidental shorts and potential damage to the car’s electrical system.
Begin by removing the fuse panel cover and the passenger-side cover using a pry tool. Next, locate the three 8mm bolts securing the kick panel under the steering column: one behind the fuse panel cover and two underneath. Remove these bolts and carefully pull the panel back to disengage the tabs. Disconnect the OBD port and any lighting connections. Remove the glove box, which is held in place by nine 8mm bolts (some underneath and inside the glovebox). Be cautious, as the glovebox will fall once the bolts are removed.
To remove the radio, insert the appropriate Audi radio removal keys (rounded side inwards) and gently wiggle each side out a little at a time. Avoid pulling straight out. Once the radio is free, disconnect the three harnesses, the antenna, and a small, fourth antenna-like connector (this will not be reused).
Wiring the Microphone and Aftermarket Stereo
Route the microphone wire under the headliner, down the passenger-side A-pillar, and under the dash. A plastic pry tool can help tuck the wire into the trim.
For switched power, run a wire from the radio cavity under the steering wheel to the fuse panel. Use a quality fuse tap (not the one included in some aftermarket kits) to connect to fuse #36. Connect the other end of this wire to the red wire on the head unit harness with a posi-connector.
Connecting the Harnesses and Testing
Connect the wiring harnesses to the Metra adapter and the head unit. Bose systems will have two filters; non-Bose systems will have one.
Reconnect the battery and test all functions: power, speakers, dimming with lights, parking brake functionality for DVD/Bluetooth, and antenna reception.
Finalizing the Installation
Once everything works correctly, secure the radio, tuck away wires, and reinstall the glovebox and kick panel. Connect the parking brake wire to the striped brown wire on the parking brake switch (located in front of the rear ashtray). This ensures video and Bluetooth features function only when the parking brake is engaged.
Adjust the display illumination to match the Audi’s red lighting and equalize the sound to your preference.
