And for the umpteenth time you can't charge the system to a value on the refer pres sensor on the benz system,it is a variable load system,the values could range from 5-17 or so at a set temp,based on demand of the system.The only way not to guesstimate the charge would be to pull it,reclaim it,charge the system by weight of 134a as indicated on the tag located around the ecu.
ohlord
Run the a/c diagnostics,post the values and lets take it from there...........