There is MB 6 step procedure to check the compressor clutch engagement. You can go to
www.alldatadiy.com and get the document.
In general, it consists of a series of tests, which elimintate componets like the AC Push Button Unit, Compressor speed sensor etc.
To answer your question, you can remove the AC compressor control relay (also refered to as the Klima relay) and bridge pins __ & __ (you will have to use the search function of the forum as I cannot recall, I believe it is pins 5 & 7).
The AC worked fine in my 94 E320 if the pins were bridged, otherwise, the compressor clutch cutout soon after engagement. It passed all the tests expect the speed sensor resistance value. In any case, it turned out the 3 wire electrical connector on the compressor was bad. Replacing the connector fixed the problem.