I have a 2002 A6 2.7 Quattro that has a great symphonic system but the AM radio does not receive signal. CD changer works great, FM works great, but not AM Help

suggestions?

 

There are two antenna boosters that are at the rear glass at each C pillar. The one on the right is the FM booster and the one on the left (drivers side) is the AM / FM booster. They are known to go bad, are easily replaced and not cheap. There are a bunch of used units on eBay but I’m not sure how to trust they work.
To get to them you must remove the “grab handle” that is in the roof area above the door and the clothes hanger tab (for lack of a better description) just forward of the grab handles. The interior trim can be pulled down to expose the booster. There are two connections. Good luck.