Hi,
I have a 2000 audi a6 2.8 manual that was built in germany. The ABS light comes on intermittently, similar to what you have described, except mine is totally random. When the ABS light goes on your ABS IS NOT WORKING, when it winks off it is working.
I left the car with a mechanic for 4 days to finally track the problem down.
1) the ABS pump is fine
2) when the light comes on you get 2 codes, one for a build up of brake fluid on the wrong side of a piston ( which you would expect when it stopped working mid operation) and the 2nd for a disconnection with the instrument panel....
Now interestingly enough the Air Conditioning is in the same loop, but I haven't found any kind of relationship there with turning the AC on and off and the ABS coming on or off.
Lastly, the airbag light came on when these problems flared up. That is interesting as the airbag light came on about a year ago and the audi mechanics couldn't find out why, so cleared the code and sprayed some conductive gunk on it.... the air bag came back on after about a week and so on, until finally after taking it back 3 times it stayed off for about 8 months until this ABS problem came along.
So, my guess is that there is a short between the instrument panel and these two systems
Short or no short the computer shuts down the ABS when it lights it up. So trust your display. you can feel the ABS stutter when, say, you are stopped in traffic with the brake on and the ABS light winks off.
Also I have had the ABS fail in snow while I am braking, but begin working again almost instantly. :blink: I think that is brake fluid build up talking, but always the display doesn't lie. If its not lit up, the system is working, if it is lit up the system is not working and drive to suit.
At the moment I am trying to trace where this short is before I take it into the dealer, as 1 week at 90 USD per hour is a bit ridiculous
cheers
<_<