Norm, recently had a new evaporator and a rebuilt compressor installed in our 1998 E320 which would only hold a refrigerant charge for a month or so. Our local MB dealer did the job for $4,000 ... expensive, but well worth the money for the job to be done properly the first time. Our 1998 E320 is in mint condition with low mileage so it made sense for us to spend the money. Your vehicle's condition may dictate another less expensive temporary fix ... like recharging the system regularly.

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Fred Hoelzle