The windscreen wipers on my 1989 have stopped working. At first it was a bit of an intermittent fault. The wipers would on occasion stop mid way through the sweep and continue a couple of seconds later but they have suddenly stopped altogether. I have a hunch that it is the switch. I wanted to change it anyway since the vehicle has very recently been treated to a rebuild and the rubber boot of the switch is looking horrible but how do I go about testing it? What else can go wrong apart from the switch or motor?