First off I'll say I havn't much of a clue as to how to work on cars but I've been able to figure out some of the following..

I have a 1997 A4 2.6 that starts to overheat only when I have the a/c on. I've checked to make sure the fans are both working properly and they are. When I'm driving the car it doesn't have a issue and blows cold air. When I stop for 2-5 minutes at a light I'll feel ambient warm air from the a/c and the temp will start to rise. Any ideas on what to check next?

I assume that the next step should be to flush the radiator, check the thermostat, and then if all is good there change the water pump. Is that right or am I missing something?

Where excatly is the thermostat located on the car? pictures or diagram would help since I'm a idiot when it comes to this stuff..

Thanks in advance for your help!

 

the coolant has nothing to do with a/c. it could be the a/c compressor. check the r134a level first.

the thermostat is right behind the waterpump though. also change the temp sensor

 

I think your fan clutch is bad. To check it, with the engine off go in the engine bay and try to spin the fan clutch by hand. If it spins with not much resistance then it's bad. It should have resistance.