Audi Repair: Audi A4 air conditioning, 2002 audi a4, audi a4

Question
Hi.  I have an 2002 Audi A4 and it sounds as if there is a valve in the air conditioning system which is permanently opening and closing.  It's definitely something to do with the aircon because if I remove the fuse the noise goes away.  The aircon works OK but the noise is pretty irritating!  Any thoughts?
Thanks in advance
Chris

Answer
Not sure what this noise is, does it come from underneath the dash?  Can you make the noise change by selecting different air flow, or moving to other vents?  Is it the compressor switching on and off?  If so it could just be due to low refrigerant.  Let me know a bit more detail,  Jan