Erratic turn signal operation can be a result of a failing turn signal flasher relay which will require replacement.Google+
Car Problem Reports
Volkswagen Passat TDI Flasher Relay Failure Can Cause Erratic Turn Signal Operation
Volkswagen Passat TDI Problem
Average Mileage: 154,000 mi (150,000 mi - 158,000 mi)
Visitor, 2004 Volkswagen Passat TDI, 158,000 mi
Turn signal relay operates erraticly after turn signal switch is back i the off postion.