keeping with tradition of usenet ... i will contribute via summary and by compilation of my research in a reply to my own question.
One can convert but there are potential problems that can be lessened by following the outline/guideline below
To properly convert an automobile A/C from R12 to R134a one should do a little more than just buy a R134a kit and install. Depending n the A/C system this may work for long time or fail prematurely for lots of varying reasons such as leaks, contamination, incompatible lubricants etc.
These extra steps will serve to address legal environment issues, longevity of service and produce a more efficiently functioning system:
* ** * DISCLAIMER * ** ** * I am not an A/C expert. Note this is ***just an outline*** and lots of details are left to the individual to determine. All this information is available through online searches. This may not be applicable to all makes of cars.
!!! NEVER !!! force fluids or compressed air through the A/C compressor or it may be permanently damaged !!!!!!
* ** ** ** ** ** ** ** ** *
have existing R12 evacuated/recycled by some proper R12 recovery device possibly at some auto shop
remove A/C compressor from car and drain all the R12 lubricant ( mineral oil )
flush R12 A/C lines with an A/C solvent to remove residual oil and gunk
replace all the A/C fitting and compressor manifold O-rings with the modern higher quality equivalents
Replace R12 service port valve/fittings with R134a service valve/fittings
put about 6 oz of R134a compatible oil back into the system (may differ from system to system)
re-install all A/C components
pull vaccum on the system
8, fill system with R134a to ~ %80 of R12 volume . (Eg - if A/C system holds 1 lb of R12 then put ~ 0.8 lbs of R134a)
install an R134a sticker over the R12 A/C sticker found under the hood so that no one has to remember and anyone will know by looking.
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