rear washer/wiper illumination not working
 

hello everyone!
the switch for the rear washer/wiper started playing up last night,started turning on and off ,now its off all the time.switch works,just no back light.
done all the hitech checks(poking and banging the side of the switch)no result.
i am not very good with electrics.
can you pls advice were i should start looking so i can fix it?
thanks in advance!