I would replace every bit of rubber vacuum line in there. Your evaporator is probably covered in dust and debris, and there won't be a more convenient time to clean it. Actually, it wouldn't be a bad idea to clean out the ducts and evaporator box too. Could you take some pictures for everyone?

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1982 300D, black w/ palomino leather, 203K
2001 E320, champagne, 105K (Mom's)
1999 Dodge Dakota, squeaky & battered, 142K