V71 is common problem,
It's the name of the recirculation air flap motor for the climate control.
What happens is over time they:
1) can get sticky from lack of use
2) They loose their correct positioning (fully open or fully closed) due to the motor slipping a cog.
Slipping a cog could be because someone's used one of those horrible aircon cleaning sprays , which leave a forever sticky residue on every bit of plastic they come in contact with - ie the rubber seals on the recirculation flap. If the flap sticks, and the motor operates, u could get a slipped tooth on the motor, so the positioning becomes incorrect, and then eventually that's why you start hearing clicking, as the motor tries to push past the fully stopped position of the flap everytime the recirculation motor starts...
So having said all that, you gotta use vagcom to get the system to relearn all the flap positions (Sadly this isn't something it can do automatically). Once the system relearns, then it's possible that the V71 motor will work correctly.
But if the v71 has been left too long, and mashed up it's internals, then only thing is a new motor, which is a bit of a bitch to get to!