Hi I have an R470 Scania with a fault on the wiring ,First thing in a morning or after it has been stood for a while everything is ok , but run it for an hour so and the horn doesn’t work ,spots ,front fogs and rear fogs control; does work ,neither does the washers , Stop turn the ignition off and the everything is fine again for a while thought it might be the aux light switch , changed that still the same , Could any one shed some light this for me