You pump down first, check to see if it hold vacuum. Then charge to 200 psi of nitrogen to check for leaks. Nitrogen will absorb any moisture (humidity) in the system. Moisture+freon=acid that will eat up your seals, causing premature faiure.

Also, testing pressure with nitrogen is a helluva lot cheaper than testing with r12. You would never want to actually run the system on nitrogen.

Once you see the system will hold 200 psi of nitrogen overnight, you pump it down again, and then recharge with freon. (r12 i would hope.)

I changed my compressor 2x, reciever drier 3x, flushed 2x. Finally I changed the evap,expansion valve, o rings galore, compressor, rec/drier, condensor. It has been working flawlessly since.



It seems with these cars once you fix on part of the system, the other side will go out.

__________________
Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2