Just like the title says. This company called Fox Tool & Supply ( http://www.foxtoolsupply.com/cart/ ) sells an A/C tune up kit for $40 that works with both R134 and R12 but I don't know what my car uses now so I don't know which hose to order.

 

There should be a label on the compressor stating the required charge, but here's a place with pictures of the different fittings: http://www.sadik.net/nissan/howto/ac.htm

 

It should be R12 unless it has been converted.

 

My 91 had r12 in it,which apparently is banned here in uk,but i think its still available to you guys,but get a bypass pulley and save some weight and power!

 

I went and looked yesterday and the label says R12 and I doubt it's been converted since the AC didn't work too well when I got the car and now it only blows a little cold air for about a minute then its worthless. I don't use it often but I would like it to work for those days the windows can't go down

 

My 91 had r12 in it,which apparently is banned here in uk,but i think its still available to you guys,but get a bypass pulley and save some weight and power!

 

Maybe you should get an A/C shop to remove the remaining R12 from your system first, & then recharge it yourself with the Fox Tool & Supply kit as it is a propane/butane mix and A/C shops won't reclaim contaminated R12.
My own A/C has no pressure and I have missed that option on a few occations, so since R12 is so hard and expensive to get I have been thinking of charging it with this HC mix instead. I don't think it is as dangerous as people first tend to think. It's been used in homes and trailers for almost a century with few accidents, plus you'd smell a leak long before an ignitable concentration is reached. R134a is flammable too, plus it's odorless and poisonous so there's no way I'm putting that into my car..
There's no power loss from having the belt on the compressor unless when you are actually running the A/C, and most people could benefit more from losing those 20 pounds personally btw...

 

That's exactly what I was thinking of doing after reading that page saying mixing coolants was illegal and dangerous.