What RWDPLZ said plus There is No "Universal" of anything that mix R134 or R12 including "Replacements" like "Freeze 12" and others posted here.
USEPA and related agencies worldwide labels Many refrigerants as Ozone and Global Warming Safe
BUT most USDOT and related agencies for Vehicle Safety Standards only allow R12 R134 and New vehicles
built specifically for it R1234yf. If you have a wreck with anything else loaded in the car's AC and have a fire or worse you can have big legal problems with police and everyone and their families that's hurt or killed.
R12 is nearly impossible to get at most AC shops now. Is banned for public sales in most countries for 20+ years. When legal for pro shops to carry it in some countries, Shops simply stop keeping equipment to use it because takes too much space and money to maintain etc for the low volume sales. Every refrigerant needs a complete setup to handle each type costing Thousands of whatever money for them. Many Techs don't even certificates to legally get R12 now.
R134 is available but may not be legal for DIY use in many countries.
Fiero and other old cars can be "upgraded" to handle R134 and work very well but is not a direct replacement and 30+ year old cars often need a lot of work just to recharge even with R12 and not leak out often in days or weeks. For a few that just add charge fittings on R12 cars and dump R134 in the system and get away with that for a year or more... Thousands of others leak like hell and stop working much less than a season. Many only want cheap fix to sell the car. Others dump cans every season then junk them when tired refilling them. Or have problems w/ R134 oil and water because Most R12 Driers can't handle R134. That can cause "Black Death" when the compressor Dies.
To give a clue, I wrote this pushing 20 years ago when it was easier to convert a Fiero... See my Cave,
AC ConversionBecause of this Most AC shops now won't touch a car with a conversion or even do a conversion because can take days to fix all the problems only for a old part to fail soon. If you find a shop to do this expect to cost a lot. Many sell or junk much newer cars when AC has problems because of cost and I'm not talking about conversions. Recently traded 10 year old car because AC parts alone was pushing $800us. One bad part was behind the engine and very hard to remove. If a temp sensor in the AC box under the dash was bad too... you have to tear apart most of the dash to get at the box and that eats many expensive Labor Hours.
I don't like most AC "Sealers." Most simple fail to seal just the hoses because "rubber" is too far gone to help. Many leaks are compressor shaft or "Bad" compressor case and no sealer will help that. Worse, Most don't read the Directions either... Sealers to "fix" metal parts use moisture to seal and any water in the system will quickly ruin the whole system.
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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave
