I just bought an Audi A6Quattro 1996 in February of this year and now noticed that my A/C doesn't work.
My friend who is a mechanic and knows a bit about cars looked into it and is not sure where is the valve that you use to charge A/C to this Audi. He is a car mechanic that has experience with US cars but not Audi's. Can anybody help with my question?

Thanks!

 

I honestly have no idea where the valves are myself, but it's like 35 seconds to find out, by just looking over the lines. The high side is usually more thin, at least at some places, if it's not marked.
Some may dissagree but If you mechanic can't find the valves he is not qualified to do the job. Don't even let him toch the car, he might hurt himself. I would recomment taking it to some independent AC place (multimple places even better), to get few opinions and price quotes.

If your AC is empty it's probably leaking, besides the car is 11 years old. So simply charging it will not help (at least for long). System must be sucked-out with vacuum pump (using real manifold gauges) to check for leaks, if there is none, you can try charging it to see if it works. On my car there is no sightglass through which freeon can be seen moving in the canister... So I've no idea how to check things further in this case [8D] (when you can see freon flowing, you can diagnose if something else is broken based on it's appearance)

AC is one of the most expensive thing to repair =)
Good luck.