OK, yesterday I found time to strip the tailgate lining, and get the tailgate window open, but I fell at the first hurdle. I put a multimeter on the solder pads and there is no short when I press the switch. I even managed to unplug the switch from its connector and test there. I have a faulty switch. Try as I might I cant see any way of unclipping the cover of the switch housing around the rear wiper assembly. Any clues? Thanks.