14-02-12, 08:56 PM
I agree with richfzs, dismantling and reassembling the right hand switch unit is a fiddly job... but in this case I think it would be worth doing. With the switchgear making intermittent contact there will be arc damage to the surfaces that is best cleaned up with a fine file or emery paper and the moving parts could do with grease as a lubricant, WD40 really isn't up to either task.
Looking on the bright side, at least without the starter motor operating at random it should make life easier for the battery!