Kinda OT, but my lurking has shown you to be a quite knowledgeable refrigeration tech. I was just stuck with an AC compressor replacement on a Ford (Tecumseh FS10, R12). Due to financial constraints, I was forced to acquire a salvage-yard unit as a replacement. The replacement (paid $12 for the whole deal, clutch and all!) came from an R134a system; I was unable to locate a unit from an R12 implementation. As I had no desire to retrofit the vehicle (it still had a full charge), I dismantled the replacement compressor, cleaned out the PAG (with brake cleaner, no less...) and reassembled with ester.
As the replacement compressor was necessary due to a pulley bearing seizure that mangled the nose casting (as opposed to an internal failure), there was no metal or other debris introduced into the system. Can I expect this (admittedly hack-job) fix to actually work when I have it evac'd and recharged? The compressor appears on all counts to be identical; I didn't even notice a pressure relief valve on the compressor--I assume this must be located elsewhere in the system (?!) and therefore not a concern with the unit replacement.
I've switched several vehicles to 134a, but always after a compressor failure. I've never tried to switch using an existing compressor back to R12, so any comments are much appreciated.
Thanks for your time, Mark Shollenberger