Looking at buying this car, but the AC is not charged. I've read about converting to the new style refrigerant but is this mandatory or can the old style still be serviced and refilled (assuming that is it's only problem)?

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1979 300SD 83k miles Astro Silver Metallic/Black leather #3447
1990 350SDL 202k miles (3L engine from an 87 300D)Black/Grey leather
2006 Pleasure-Way Class B MoHo (Sprinter chassis) 134k miles
2005 E320CDI 270k (car is sooo fast - I can't believe it's a diesel!!!)