Please say it ain't so!!!!!!
Contaminating the R12 that was in there without so much as evacuating is bad news. If this were an old beater on its last legs I could understand, but this is an MB that I assume is a decent car.
If you want a/c you need to look before you leap. There are plenty of posts on here that will describe how to properly troubleshoot the system without contaminating it just to see if the clutch will kick in.
You really now need to completely disassemble everything, flush, replace the filter drier, drain the compressor, put on 134 orings, evacuate and charge.
Had you not done this, it would've been a simple matter of finding the leak or problem, repairing it and recharging with R12.