TraderAlex

Hi

I am wondering if anyone over in this forum, since I am not getting any resopnses over on the a6 side. I beleive the automatic climate control systems are similar between the two models-

I have about 85,000 miles on my '00 A6 Avant 2.8L.
I have a noise coming from under the hood, that seems to be related to the climate control system. I have heard it since the car was new, but it seems like it is now more pronounced, especially in cold weather. The best way I can describe it is tht it sounds like a ringing sound with a rasp. Typically, the noise faded quickly after vehicle start-up,.and heard usually in winter weather. But the ringing sound is lasting longer The key here is that the noise goes away when I switch the automatic climate control to "off", then all is normal. Turn the climate control back on to Auto and the noise comes right back. But once I drive the car a number of miles, and the temperature gauge works it way up to around 250F, the noise is then gone for the duration of the drive, until the next time the engine has cooled down. Heating of the interior is otherwise normal. Has anybody else experienced this, and can anybody advise what I am dealing with? Just Another of the many A6 quirks, or something else?

AudiMick

I would assume that when you turn the climate control to auto you are switching off the AC.

So if the noise goes away, I would it's something that is OK when the engine compartment is warm.

The secondary electric fan and AC compressor + clutch are possible causes.

Kris Hansen

The AC compressor on my A6 is VERY loud, but the AC compressor is not temperature related (other than not running at below 32f).. it will cut on and off periodically though. I wonder if that's what you're hearing?

TraderAlex

Too bad we can't add sound clips, here. Whether it is the A/C compressor depends whether it tries to kick in as part of automatica climate control at start-up, even when it is freeing cold outside. This used to be a few seconds event. But what I am doing right now is starting up with the climate control swtiched to off position. After a few miles and engine warming, I swtich it back on without hearing the offending noise. Best way I can describe it when it happens is that it sounds like an annoyng bell or ringer.