I just got my 99 grand cherokee a week ago. The second day I had it the gauges started acting up. They all die and the warning lights come on the same way they would if you rolled the key forward without actually starting it. When this happens the Windows, locks, and stereo controls on the steering wheel stop working as well. Sometimes it does not recognize that the door is closed and sometimes the overhead display doesn't work. So far all I have had time to do is check the wires that come out of the cab and go into the driver's door. A wire has been replaced but i took the tape off and used solder and heat shrink. I have found that if disconnect the battery for a short amount of time the electronics start to work again... Until they decide to give up. Please help!

 

The last time I had heard of someone having this issue, they had to replace the computer. Given the amount of electrical failures going on simultaneously here, I'd say that's a good bet.

I would start by locating the ECU and checking for signs of moisture. If water has gotten to it, I'd start looking for a new unit.