The headlights are important safety features on your Audi A4. Malfunctioning headlights on a vehicle can be very dangerous, as you will not be able to spot hazards on the road, and other vehicles may not be able to see your vehicle in dark conditions. Changing the A4's headlights requires accessing the headlight assembly in the engine compartment. The A4 uses a single H7 bulb for both the high beams and the low beams.
Turn off the A4's engine and engage the parking brake.
Raise the bonnet of the A4 and remove the plastic cover over the power steering reservoir, if replacing the headlight on the driver's side. If replacing the passenger's side headlight, remove the air intake tube that runs from the grill to the intake box by removing the two screws holding the intake tube in place. Remove the engine compartment trim panel for models manufactured after 2007.
Remove the four screws holding the headlight assembly in place--you will find two located at the front of the headlight and two at the back. This will loosen the headlight assembly.
Unplug the harness and pop off the wire loom attached to the assembly. Lift the assembly out of the vehicle.
Unclip the back cover on the headlight assembly and pull out the old H7 bulb. Use a clean cloth to install the new H7 bulb. Do not touch the glass portion of the bulb and do not use anything other than an H7 bulb.
Place the assembly back into the engine compartment of the A4 and reattach wiring harness and wire loom. Reinstall the four screws and place the power steering reservoir over (or place the air intake tube back into the vehicle). Close the bonnet.