I'm starting a project to reinstall my aircon into my Miata. I originally had it in the car, but removed it about 5 years ago. I kept all the parts and left the electronics in the car. I am going to try to document this and will edit the posts with pictures as I have them.
That system had been converted to r134a when I lived in Charlotte.
Removing it is something I have regretted.
Anyways, I bought a complete system used from a '97 about a year ago with the intention of installing it in my car. Physically, the two systems are similar. The 94-97 systems came from the factory with r134 as the refrigerant, previous years was r12. r134a, according to the info I have read is about 80% as efficient as the r12, but is still very effective and less harmful to the environment.
Moving from California back to NC has moved this project up as a priority. I will also use it to diagnose and gain some practice so I I can fix the AC on my wife's '99.
Another difference I found between the NA6 and the NA8 is in the wiring. Fortunately, since my car already has it in place, I won't need to lay in the harness. The NA6 uses one relay to control the clutch on the compressor and also to turn on the condenser fan. On then NA8, there are two separate relays; one for the compressor, one for the fan. The pressure switch is also different between the NA6 and the NA8. Fortunately, I just tested the mounting ports and the NA6 switch will fit on the NA8's line.
(insert picture here)
Right now, all I am doing is surveying my inventory: what I have, what I need, re-familiarizing myself with where the lines go, how they attach to the chassis, etc.
I have been looking up parts online to see what crosses over between the two systems. Although I have the complete systems, there is stuff I plan to replace just because "I'm in there". Fortunately for me, too, the previous owner of the NA8 system sealed all the orifices and openings as he removed it. The compressors are a little different because of the refrigerants. The driers are different, the condensers are the same, the expansion valves are the same, the evaporators are the same, the pressure switches are different, the o-rings and seals are the same. I haven't looked at the hoses (the flexible ones), but I am not planning to replace those.
Right now, I am planning on replacing all the system's o-rings, seals, dryer, expansion valve, and pressure switch. Altogether, it's about $100 in parts. I will use the NA8's aluminum lines with the NA6's pressure switch. I will use the NA8's evaporator because is 5 years newer and has been sealed. I left my evaporator open to the engine bay and I'm sure 5 years of dirt, dust and crud has ruined it. I think swapping them out won't be too difficult.
In the meantime, while I order parts and assess the install, here's is good OE installation walk through:
http://homepage.mac.com/akerman/misc/90ACINST.pdf