Additionally, when taking vehicle to a professional a/c service, fist thing they do is evacuate the a/c sytem, pull down to hard vacum & do a drop test. This accomplishes two things: checks the system integrity and removes non condensible gases. Once this is accomplished, they re-fill systen with a known amount (by weight) of hfc134A refrigerant & pag oil. Pressures alone don't tell the complete story about the condition of automotive a/c.

Good info Mark.. I agree pressure doesn't always tell the whole story. However..I've found through manual reading that our cars don't seem to fall into the "normal" pressure ranges. ;)

Thanks for all the info folks. I finally got a little time on my hands so I can go out and mess with it again. I hope I just need to fill it up some more.