One problem related to tail light switch has been reported for the 2009 Audi A8. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2009 Audi A8 based on all problems reported for the 2009 A8.
Multiple component failures relative to tail light assemblies. Both trunk mounted tail light assemblies were replace in 12/11 under manufacturers warranty. Sealed tail light assemblies were not water tight which caused failure of circuit boards and led lights. One of the two replacement units has also failed again (18 mo. In service and 6000 miles) lights have failed in this unit as well, causing potential hazard due to lack of illumination experienced identical failure on my 2007 Audi s8 which is the same chassis platform as the vehicle above. A total of four of these tail lights have failed on these two vehicles. There were no collisions or events that would have caused damage or affected the integrity of the lighting unit . Appears to be a design or manufacturing defect. In reviewing some of the Audi chat boards, this is a common failure on this d3 platform.