I have a 1999 Grand Voyager with a 3.3 liter engine. Twice now, the instrument panel has shut off: all the gauges fall to zero, as if the ignition switch were off, except for the speedometer, which shows an increase in speed until it pegs out at the high end. Nothing else is affected. This happened once in daylight hours (without the headlights on) and once at night. Both times, I continued driving. The first time, it corrected itself. The second time, it sat for a few hours, and when I started it, everything appeared normal. Any suggestions?