[The Newell]

Any electronic read out will have a sending unit to transfer vehicle information to whatever gauge or display that it is sending info to- usually a dashboard will include lights, speedometer, several gauges too read fuel level, engine monitor gauges etc.- if something is wrong with the power to the dash or there is a short circuit etc.- then the whole dash usually goes awol- if the problem is only with one section or display then look to that specific area- its the same with electrical (12 volt) if everything works on a coach but the starter on the generator is not working correctly then look there- same with a dash display - on all computer controlled vehicles there is a vehicle speed sensor (VSS) and it sends the vehicle speed readout to the speedo to your dash- in many applications this sensor also calculates miles or kilometers per hour- if your speedometer reading seems accurate then it may also be the actual mileage display in the dashboard- To be honest I think it would easiest to order a new VDO or repair it as Richard mentioned.