passat 2002 rattling noise when heating

There is a rattling noise coming from the front air vents? when the heating works, it stops immediatley when i turn air-conditioning off. Never happens when cool air comes in the car. Any ideas?

Hey, I have the same issue, did you ever fix it?

could have some leaves stuck in the vents, its easy to get leaves in the ducts when the pollen filter is removed. Is it a weak tapping noise? if so the blend air doors may need to be reset to basic setting, its done with a vw scan tool.

Hey! That's exactly what it sounds like, does that mean I need to take it to a VW dealer who has the scan tool?