I agree that the first thing you need to do is get gauges (which you stated you have on order). You can then reasonably determine how close to a full charge or how low of a charge your system has. You can also jump the compressor to see what the pressures show (assuming you have a reasonable charge). But in all likelyhood your system is very low, thus the reason the compressor is not spinning.

If the system is low, it means it has a leak. If you want the AC charge to last for more than one season (or perhaps even a few weeks or days) you should really fix the leak.

I bought a recycle machine like Larry and John have talked about. I got it cheap off of Craigslist along with some other AC tools. You just have to be on the look out. They are out there for reasonable prices. Many shops want to get rid of them as they no longer service R12, that is how I picked up mine.

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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