You got one in before I replied . You have found your problem. You will need to get the system checked for leaks. You're suffering from low refrigerant pressure, hence the low pressure switch cutting off the compressor. See, that wasn't too bad. BTW the W124 is noted for leaking evaporator cores. So have your tech start there and work his way back to the engine as these are sometimes the most difficult leaks to pinpoint.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE