Hey everybody!

First - here are my vehicle deets:
1. Year of car - 2006
2. Model of car - A3
3. What engine & TIP or 6sp - 2.0T - TIP
4. Miles - 137K
5. FWD or Quattro - FWD
6. Any CELs or stored codes - Not pertaining to this problem.

So I noticed this evening while the car was idling that there is, what I can best describe as, a rhythmic sort of whirring sound that occurs while the heat is on. Its pattern in seconds is 1-0-1-0-1, etc. As soon as I shut the HVAC system off it stopped completely. Turned it back on and it started up again. I couldn't really tell where it was coming from while inside the car so I popped the hood and took a listen. I could hear it out there too. I took to the Google machine and couldn't exactly pinpoint the issue. Could be the blower motor bearings I suppose, but it didn't seem to explain the noise under the hood. Any assistance is much appreciated!

 

I have the same problem and have been told its the AC pump. If I push the Econ button it stops completely. So, that's what I do to run my heat until it goes into the shop in a month.

 

I think you've nailed it. The clutch on the compressor is engaging and disengaging in cycles. Once you hit the Econ, that tells the Climate Control not to use the A/C compressor (which can also be used to create heat). Probably just needs a charge.