If you have the system dissassembled, first thing to do is put a conversion kit for R134a. I would also get a new accumulator so you have fresh desiccant.
Once it is all together, you need to vacuum the system for 30 minutes to an hour to make sure there are no leaks and remove all moisture. From that point, you charge it with R134a, and PAG oil. That should be it.
You won't find R12, and if you do you can tell the price difference. R12 is ~$80-$100 a pound, vs. $10-$15 a pound for R134a. Make sure that it says "automotive" and R134a somewhere on the label, there are lots of knockoffs on the market and some can be flammable.
PAG oil is used for R134a systems vs. Mineral Oil in R12 systems. You probably won't find it either, so no need to worry about that.
As for specific amounts of refridgerant and oil, some of the others will have to help you out, or find an AC shop to help you charge and lube the system.
Also, how is your orifice tube? Its worth replacing as well, they are just a few bucks.
[This message has been edited by BlackEmrald (edited 08-07-2013).]
PAG150 - new compressor with R-134A, GM recommended.
The Fiero A/C system oil capacity is 8 oz.
If you are buying a replacement compressor, get the newer style HR6 unit, which is more suitable for R-134A, than the older style DA6 compressor.
Also, if you need to turn in your old compressor as a core, make sure you remove the Red and White switches on the back side before turning it in, as you will most likely need to install them on your replacement compressor.
[This message has been edited by hdryder (edited 08-07-2013).]
Honestly, as I go back and read this thread, I realize (and don't take this the wrong way) that you can't know what you are doing if you don't know the difference between R12 and R134a. There is a reason AC work is expensive to have done, it is precision and there is a lot that can go wrong. To much or to little refrigerant and your AC won't get cold, improperly lubed O-rings and you have a leak ect.
What I would recommend is, do all the nut-and-bolt stuff yourself. Replacing components ect, but let a shop assemble the lines and vacuum and charge the system. AC shops have verrrry expensive equipment to do these types of things, so they will get it done right the first time.
I want to make it clear, that i'm not doubting you or your abilities, I just know from experience (I am EPA certified) that a lot can go wrong if you don't know what you are doing, and the dollars add up quickly.
I know you can tell the difference between r12 and r134a systems by the connection, but I don't know what the difference in the connection is.
R12 fittings are threaded, R134a are quick-disconnect.
and where is the orifice tube?
The tube is located in the high pressure line just below the accumulator and blower motor, just towards the passenger side from the high pressure service port. You can see it here (this picture shows a non-factory switch installed at the high pressure service port):
I was planning on just getting everything all flushed, and then vacuum checked.
Unless the compressor had a mechanical failure, you don't need it flushed. You also don't need to replace all the o-rings in the system, just replace the ones that are disturbed.
Install the new compressor, use PAG150 oil, put 4 oz into the compressor, put 4 oz into the suction side of the accumulator. Draw vacuum for an hour with a good mechanical pump (not one of those "venturi" style pumps, they usually cannot pull a strong enough vacuum) to boil out all moisture. Then charge the system with R-134a. In a pinch, you can use Ester oil, although that's not what GM recommends. I had it in my system for a couple years and it worked fine.
If I was going to go through it all, Id need the part number for a new style compressor, I don't know the difference between the new and old style ones.
This is a DA6 compressor (the wrong one): FOUR SEASONS Part # 57655 This is the HR6 compressor: FOUR SEASONS Part # 57255
[This message has been edited by masospaghetti (edited 08-08-2013).]