2003 C320 coupe, 2000 ML320
The low pressure switch should have kept it from running even though you had it switched on..
I used a scanner, no codes for the A/C.At the minimum, you need a vacuum pump, a gauge set and a MB scanner.. Prices start at about $250 for the cheapest ones out there.. Most important,.. you need the knowledge "how to service an AC system,.. Must be hundreds of videos on Youtube on this subject..
OR,. call around and find a independent shop that will do it for less than $500