I have a 1984 Ford 6610 diesel 4WD with Hi/Lo range. The fuel gauge and temp. gauge peg to the right when the lights are turned on (engine off), and also whenever I start the engine. Removing the cluster illumination lamps from their mounting (ground bar) solves the problem when the lights are turned on. I suspect a weak ground for the instrument cluster. One ground wire from the cluster seems to tie to the 4WD switch and other to the Hi/Lo range switch. Does anyone know where these ground wires find ground on the chassis? There is too much loom and tape to trace them out visually. Any suggestions on how to approach this situation?