Does the 240 have a hand brake? I ask because I don't know.
What I do know is on the 108 I had a flickering brake light. Only thing I could find was the parking brake cable needed adjusting. I could make the light go out by pushing the hand brake handle toward the dash. When the cable gets slack the spring will keep the handle from engaging the switch.
Check it out.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.