Before you start tearing the doors apart to replace the switches, try turning the child proof switch off. On the 560, I found with the child proof on, the rear switches have no power and do not illuminate the mini bulbs in the switches.
'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.