I don't know that you have a charcoal filter, but you do have cabin air filters. They are located below the windshield. You have to access them outside the car under the hood...They are challenging to get to...
We carry the CD rom for repair for this 124 chasis car and the filters in partsshop.
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM