here is someone talking about the same thing on Audizine: My owner's manual specifically states that the cruise control system employs Active Braking to maintain the set speed.
I am assuming this means going downhill, it will use the brakes to maintain the speed, since the transmission won't downshift to use engine braking. My cruise control does not do this.
I took the service adviser at my local Audi dealership on a ride, where we were going 65mph down a hill with the cruise control set at 50mph. She told me that wasn't how Active Braking worked, but couldn't explain how it actually worked. I told her that a cruise control system that cannot maintain a set speed is useless. She then tried to blow me off by telling me that the owner's manual is generic, and the features do not apply to all vehicles (duh). I asked her to show me where it says it's part of a package or an option, and she couldn't. She proceeded to tell me that if the brakes are overheated, the system will not use Active Braking, which is true. I find it hard to believe that the brakes would be overheated when I'm barely using them, and every time I go down this hill.
I just want my cruise control to work. I have reached out to Audi USA to find out what their definition of Active Braking is, and what parameters are necessary for it to engage. But please tell me I'm not crazy, and it should be maintaining speed downhill - somehow...