Charging with nitrogen is a whole lot cheaper than r12. Pressure testing IMO is the best way. 180psi solid for 24 hrs = victory.

I'd throw 1 can of 134 with some dye in it and check the leaks with a black light. Once it cycles a few times the dye will show.

I charged my car 4 times with nitrogen before I found every last leak. My ac is still ice cold.

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Eugene

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