is the shop going to flush?
reciver dryer changed?
correct amount of mineral oil for R12?
long vacuum?

observe what they do and for how long, you may be surprised.

R134a Pag oil absorbs alot of moisture, more than mineral or ester, mixing oils and refrigernants can create acids in the sytem, reason for the flush.

Autozone AC repair DVD $8.99 get one, get educated and know more than most of the $70+ per hour hacks!

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1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification