2001 A4 with 6 CD changer in trunk...spins through and detects discs but then won't play. Allows me to cycle through tracks but not cycle through CDs in changer...I do have an ipod hookup w/ a source selector but I don't feel it's part of the problem.. CD player/radio still works perfectly. WTF?

 

check the connection on the cd changer....its mite be loose...mine changer did exatly the same..i thought it wasbroken so as i was changing it out with another one...but....for mei found out that the connection in the trunk was only half way in because of the locking tap was bend so it wouldn't let it fully connected....i bend it back straight...plug it back in...and work fine now....good luck.....