Erratic turn signal operation can be a result of a failing turn signal flasher relay which will require replacement.Google+
Car Problem Reports
Audi A4 Quattro Flasher Relay Failure Can Cause Erratic Turn Signal Operation
Audi A4 Quattro Problem
Average Mileage: 120,118 mi (50,000 mi - 168,000 mi)
the turn signals stopped working although the emergency flasher still worked... the flasher relays are all in one unit located in the dash behind the red triangular emergency flasher(both the turn signal relays and the emergency flasher relays are all part of one unit)...ordered a new unit online for about $50.00, takes about 20minutes to replace
Visitor, 2003 Audi A4 Quattro, 50,000 mi
Erratic turn signal. replaced signal relay.
Visitor, 1999 Audi A4 Quattro, 160,000 mi
Erratic turn signal operation. Gradually got worse to the point that they would rarely work. I removed the hazard switch/relay above the radio. I took the relay unit apart and found there are two relays on the circuit board, the one for the hazards was working fine but relay for the turn signals would turn on and stay stuck on. I sprayed a bit of WD-40 on the movable part of the relay and now the relay/turn signals are working OK again. We'll see how long it lasts.
Visitor, 1999 Audi A4 Quattro, 130,864 mi
turn signals stopped working accept for manual opperation
Visitor, 2001 Audi A4 Quattro, 134,000 mi
turn signals stopped working although the emergency flashers worked fine... replaced the flasher unit
Visitor, 1998 Audi A4 Quattro, 146,000 mi
hazard and turn signal flasher not working
Well the turn signal use to flash once or twice and then i never worked again so then i bought a column switch and changed it and it still didn't work and now when i turn on my car it doesn't stay on and when i drive it it does not want change gears it stays in the first one.
Visitor, 2004 Audi A4 Quattro, 80,000 mi
Blinker wouldn't operate properly erratic behavior.replaced the controller.
Visitor, 2001 Audi A4 Quattro, 143,400 mi
Flashers stop working after they warm up. Do not flash after a few seconds. On and off working. Ready to replace relay and see.
Visitor, 2001 Audi A4 Quattro, 91,895 mi
replaced hazard flasher relay above radio