Dead '96

So I had my Jeep on the charger Thursday night to Friday morning, it worked just fine and I had it running yesterday (didn't drive, but started it up for about 45 mins to do some work on it) So it was running fine, then this morning, I autostarted it for about 25 mins, then when I went to leave, I got in, and the Gen light was on, and my battery was almost dead, but the weird part was, my RPM was at 0, but it was running...even when I rev'd it, it would still read 0, the dial wouldn't move at all....so I turned it off to see it if was just something being weird, and now it wont crank, batt is dead...Why won't it start now, but started perfectly fine earlier?
(It's also really cold here in AK, that might have something to do with it.)

I just went out and tried to start it again, it started right up with my autostart, but the gen light was still on and the battery was rapidly dying again.

Seems that your alternator is not charging. When voltage is low, the tach goes to 0. Had it happen on my Escort. If you have a voltmeter, you can first test your battery with everything off. It should be 12-12.5 volts. Yours might be lower now because it may have low charge. After you start the vehicle, check the voltage at the battery again. It should be 13.5 to 14 volts (or thereabouts).

Basics, sorry: Disconnect and clean battery cables and battery posts until they are both shiny. Not a bad idea to do same with grounds. If you still have the problem, take the alternator in to a parts store and have it checked. PCM controls the voltage regulation (expensive), so hopefully it's the connections or the alternator.

When the car was running, the gauge read that the voltage was dropping, the longer it ran, it was in the red. And I also tried the window wipers to test this little theory of mine, and they barely slid across the window, took about 30 seconds each side.