Early A A/C how well does it work

slantsixdan, your fear of hydrocarbon coolants sounds like the EPA's rants. BTW, when was the EPA tasked with safety? Before I switched to Duracool, I read up. They claimed an engineering analysis that if the whole coolant charged leaked into the passenger compartment in 5 minutes, it would not create a combustible mixture. They add mercaptin, so you will smell even a tiny leak, just like natural gas. Most leaks are into the engine compartment and you would need an ignition source. I doubt most cars are so well sealed that their 5 minute leak analysis is even close to valid. I did Phd research in experimental combustion, so my lack of concern has some basis. In contrast, R-134A is both flammable and poisonous, in addition to being a potent "greenhouse gas".

Your point about becoming a persona non-grata at AC shops is valid. The mercaptin smell will stay in the tubing long after you vent the coolant (which doesn't hurt the earth), so the fussy shops will finger you. However, I plan to avoid those. They started charging $100/lb for freon as soon as they could get away with it years ago. If I ever need shop work (unlikely), I'll find a shadetree guy or an amigo shop that isn't snotty with their customers.