If you are replacing a compressor, most require a new accumulator and orifice tube to activate your warranty. My compressor from Four Seasons had paperwork that specified 150 PAG. Oddly, instructions said to not use PAG to lubricate the seals and O-rings because it causes corrosion. I have a bottle of Nylog Blue that is used by HVAC people, both automotive and commercial/residential, for lubing seals and O-rings. It doesn't dry out like other lubricants and it prevents leaks. A 30ml bottle will lubricate every Fiero on the road today. It's available if you want it.
I may be telling you something you already know, but the whole system needs to be evacuated of all the old refrigerant and oil. The conversion for a Fiero uses exactly 36 oz. (3 Cans) of R134a). Four oz. should go into the accumulator and 4 oz. into the compressor. My compressor said it had 3 oz. in it when it arrived, but we drained it and added 4 oz. to be sure. With the system on MAX, the temperature should drop 40* below outside temp.
On and Off pressures are different for R12 and R134a. The R12 cycle switch on the accumulator can be adjusted for the R134a but it's much easier and relatively cheap to just buy a cycle switch for R134a and you know it's set properly. No guesswork. Or grab one off a junk yard car.
Don't be tempted to get one of the variable or Smart VOV orifice tubes. They're expensive compared to a standard tube. Mine caused the system to overpressure, then the installer had to rip the tube apart to get it out because it lodged in the hose.
