Originally Posted by EnzyteBob

You didn't need a vacuum pump to install a new compressor? How did you remove the air from the system? Are car compressors so resilient that they can compress non-condensables and survive?

I am the owner of a residential/commercial A/C company. I don't have much experience with car A/C systems, but the basics of the refrigeration cycle still apply.

In a building A/C system, air in the lines would grenade the compressor in a very short time. With some refrigerants, the air actually turns the oil in the refrigerant into acid.

I'm not sure what kind of oil R-134a has in it, but can only assume, that any kind of air in the system would be pretty detrimental to the lifespan of the compressor.