hello Iowna 1999Audi A8. was going to check the a/c refrigerant pressures because the a/c does not seem to cool very well. was goingto hook up gauges but found low side fitting to be like the old r-12 systems. Was wondering how would i go about hooking up a normal r-134a gauge. the only low side fitting i see is one on the drivers side under the vents .and its not the quick connect type, its a threaded type. I realized it is not r-12 size threads. it is bigger.
Any ideas?
Thank you

same problem i have with mine. i found that one fitting you are talking about as well, and the thread size seems to be more for a sensor or switch of some sort. it is slightly smaller than a retrofit fittting for r-12 to r-134a. only thing i could possibly think of is installing an inline filter with a service port on it. have to look more into it.