Hi I am having similar prob with my c600h. Changed ignition switch, sometimes works sometimes not. I found that fiddling with the wires on the underside of the ignition switch sometimes works. I also discovered that if I take off the steering wheel etc and remove the dash board, it works perfectly. As soon as I refit it, it stops working again. I cannot see any short circuit posibilities. Very strange. I suspect a design fault but I am not certain.
Mick H, June 2011
