Allan, Not sure if this will help or not, but I had sorta the same problem with my 2000 Grand Caravan. We had electrical problems with the rear winshield wiper as well as the climate control up front, but it also the Cluster Controls (I.e the Speedometer, Gas Gauge, but the Tach worked). We were blowing fuses I forget which one, but the fuse box under the dash right by the Emergency break. You might want to pull them and take a gander, If not you are having the same problem as I am, and have a Ground fault somewhere on that circuit. Pain in the Arse to find, time consuming etc. The only difference is that you still have control of your Instruments which I do not. Not sure if they have changed the circuit since 2000.
Best I can do to help, hopefully this helps. V/R Darrell