This is a common problem on the E Class of that year range. What happens is a solder connection to the pin that holds the switch to the circuit board comes loose and therefore gets no response when you move the switch. Check out MBCA's article in "The Star" on pages 86 and 87 of the current issue and it tells you how to make this repair on your own without replacing the switch assembly at a cost of $130.00. Good luck! Happy Benzing
Brian