Erratic turn signal operation can be a result of a failing turn signal flasher relay which will require replacement.Google+
Car Problem Reports
Audi A6 Flasher Relay Failure Can Cause Erratic Turn Signal Operation
Audi A6 Problem
Average Mileage: 120,750 mi (73,000 mi - 180,000 mi)
Visitor, 2002 Audi A6, 130,000 mi
Not fixed yet, unknown problem.
Flasher relay failure causing erraric turn signal problems.
turn signals very eratic. sometimes don't work at all.
The flasher no longer operates. The lights are working fine and the fuse system is good, but it no longer clicks and turns off. We need to manually click the light to indicate direction of turns. Annoying!