What is wrong if the speedo and tach are not working in a 1994 Nissan Kingcab 4x4 v6 and how can it be fixed?

If the speedometer and tachometer are not working in a 1994 Nissan Kingcab 4X4 V6, it could be that a fuse is burned out. It could also be that their mechanisms in the undercarriage are corroded or dirty if the vehicle was used for 4-wheeling off road.