R-134a compatability

Is R-134a universally compatible with most any automotive A/C system or are there R-134a specifically forulated for certain types of cars? My ac system on my nissan is bone dry at the moment. I'm taking a automotive A/C class right now so I want to try to charge it up myself at school (snap-on evacuator is so easy to use), and hopefully doesnt have any major leaks to complicate the project. I called and asked a nissan dealership if they carry the refrigerant for my car and they told me that they will be more than happy to take an appointment for me to have my A/C system serviced at the dealership, otherwise they wouldnt sell me the refrigerant. Is it safe to use off the shelf R-134a on most vehicles?

if its an R12 system and its empty you more than likely have a leak. which means that the 134a will leak out twice as fast cause the molecules are smaller than that of r12. the different types of oils used in each system can react and form an acidic compound. i suggest using PAG oil when refilling(6-8oz total system capacity) put a vacuum on it, get it down as close to 30 in HG, if it wont go to 28in or so you prolly got a leak. shut the pump off and see how long it takes to bleed vacuum off. if it doesnt, then charge it up with some flourescent dye added. youll probably get some noise from the reed valves in the compressor though. shelf 134a is the same stuff we carry at the dealer... but you gotta have a certificate saying you passed the epa test on refrigerant to buy it.... well check that... they should ask to see it before selling it to you

Nope, my car is a 97 so no retrofitting required. But i went to kragens anyways to buy the R-134a, and according to specs two 12 oz bottles should do. They didnt give me a hard time or ask for the 609 certification when I bought it, not that it matters cos I have the license I got through the school. ;-)