AC work is pretty simple. I had never worked on an AC system before and I totally rebuilt mine for probably around $300 (I didn't need a new compressor and the only real issue was a leaking condenser). Of course I bought some equipment that doesn't go into that price.

You have all the help you need right here.

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2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD