One problem related to wiring has been reported for the 2005 Audi A4. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Audi A4 based on all problems reported for the 2005 A4.
Problem of "dipped" headlight on my 2005. 5 A4 b7. Purchased the car used in 2009 and have had this issue since purchase. Asked mechanics to investigate but had found nothing wrong. Usually it was just one side, either left or right (both have occurred multiple times). The other day was the third or fourth instance where both sides threw the "dipped" error, leaving me barreling down the highway at 75mph with no lights. While power cycling them usually brings them back, this is completely dangerous and unacceptable behavior for a vehicle that is allegedly working properly. It is clear to me, as an engineer myself, that this is a gross short-coming in design of the electrical system used to drive the lights. Either the wiring, or ballasts are malfunctioning. Audi has done nothing to ameliorate or warn me of this issue.