Engine Replacing a/c compressor

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The original specs for R12 is 40 ounces with 8 ounces of mineral oil

With a conversion to R134A, you want to run slightly less. About 36 ounces. About 7-8 ounces of PAG oil total. You should really do a total system flush and start from scratch. The orifice tube should also be replaced as standard practice whenever the system is opened.


The cycling switch on the accumulator should also be adjusted so that the compressor cycles on and off right around 21-22psi on the low side.

Make sure you pull a deep vaccum before you charge. 500 micros or less. Don't just hook it up and charge otherwise it will take less, and you'll be replacing everything in a few years due to moisture in the system.
 
The original specs for R12 is 40 ounces with 8 ounces of mineral oil

With a conversion to R134A, you want to run slightly less. About 36 ounces. About 7-8 ounces of PAG oil total. You should really do a total system flush and start from scratch. The orifice tube should also be replaced as standard practice whenever the system is opened.


The cycling switch on the accumulator should also be adjusted so that the compressor cycles on and off right around 21-22psi on the low side.

Make sure you pull a deep vaccum before you charge. 500 micros or less. Don't just hook it up and charge otherwise it will take less, and you'll be replacing everything in a few years due to moisture in the system.
I have a full a/c compressor at the shop I work at so it does pull a vacuum before filling I just need to know if I need to put 8 ounces of oil since the compressor already has 3 Oz and I figured the system would already have some still minus what I pulled. I just don't wanna over fill with oil