At the risk of being labeled a “hack,” I replaced the York piston compressor on my AMC Matador. Vacuumed the system and checked for leaks. Charged with R134a and the proper amount of ester oil. Very little cooling. If you are obsessed with R134a, follow the author’s instructions precisely, to the letter. If you are more flexible, consider readily available R152a as a substitute for R12. The internet is loaded with information on R152a, all is positive. I tried R152a and it works perfectly! It is every bit as cold as R12, but readily available as “canned air,” keyboard duster," or “dust-off.” Buy a 4-can package at WalMart for the same cost as one can of R134a. If your hoses, condenser, evaporator, receiver-dryer, and expansion valve are junk, go with R134a and replace everything. Otherwise, keep it stock and enjoy R152a and 38 degree air from your factory air conditioning!