I have the same problem with my 2006 SWB 4Work
It's currently booked in for repair on 18th December so if it gets fixed, I'll tell you what the problem was.
If you find out a solution in the mean time, let me know
Not sure that there is adjustment on the switch and the lights work so unlikely to be the switch itself.
Posted on Wednesday 10th of December 2014Know the answer to this? Post a solution