A/C that only needs a recharge, or that holds a charge poorly, appears in listing after listing, and R12 refrigerant is noted as expensive and no longer manufactured. Door-lock and climate-control faults are almost always vacuum-related, a well-known age issue, and the A/C servo is a common trouble spot that one owner temporarily cured with a whack of a hammer.
A/C and vacuum system quirks
Mercedes-Benz 450SEL 6.9 · mechanical