Maybe you can give some suggestion on what maybe causing this.
There is nothing obvios left (on) inside the vehicle
I have a 2002 MERZ, C230 S, Coupe, 93,000 miles.
Battery and Alternator are 8 months old and yes I had them tested, results is OK
However there is a draw on the battery after 3 or 4 days (no driving no starting) of just parking only the battery will drain.
Eddy
There is no way here of determining where the parasitic voltage drain is at.
The first thing that should always be checked is for a trunk light remaining on. (a la refrigerator light)
After that, one has to disconnect the battery negative cable, connect an ammeter or test light, and start removing fuses one at a time until the circuit where the problem lies is determined.
There is no easy answer on this one but the problem itself may not be that complicated. It’s going to take someone with a mild understanding of electrics and preferably a factory wiring diagram if it gets to that point.