1999 Audi A4 noisey heater

Ok so when you turn the heat on and blower on high when does it make noise? Does it make noise on defrost? If you turn it to floor or vent does it make noise then? How car savy are you? I ask because what I need to know is if the noise only comes on when you have it on a setting that causes the A/C compressor to come on or not?

Hello thanks for your prompt reply, Heater fan setiing i.e hi or low both makes noise, Makes the noise if fans are up to windscreen, down to feet, or centre and side dash. Recirc makes noise as does demist or defrost setting the only setting that stops noise is by pressing econ mode with any of the above. I am thinking clutch mechanism on A/C compressor is not moving adequately to required positions. What do you think. Forgive my guesswork I am an amateur at this stage.

Kind Regards

Ok here is a pic of the A/C compressor the front of it has a clutch that engages with an electro magnet and that causes it to turn. So the question is does it turn on econo setting or not. If it doesn't turn in econo mode but does in all the other possitions then yes I would say the a/c compressor is bad. Let me know what you find.