Interesting electrical issue

I have a 1999 XJ Sport. I replaced the battery not long ago. Recently I have noticed that every once in a while, the voltmeter will read about 10 vDC when I start, the soon after drop to zero. I do not see any issues with the electrical within the jeep. lights work as normal, stereo is fine, engine runs well. Some times, if I shut the engine off and restart it, the volt meter moves back to 14 VDC. Sometimes when I am driving, the volt meter will drop to 0VDC then eventually back up to 14VDC. I think there might be a problem with the wiring to the volt meter or maybe somewhere within the computer modules. Anyone ever have this problem?

If the dashboard voltage gauge drops to 9 volts there usually is an alternator issue, typically worn out brushes. If the dashboard voltage gauge rises to 19 volts there usually is connectivity issue, rotten cables, loose/corroded battery terminals, loose/corroded ground points, or similar.

Yes, but in this case, the voltage drops to 0VDC. If that were true, the Jeep wouldn't get spark or run at all. The lights work just fine, the radio works just fine and the A/C works just fine. All of those would die down if the alt was wasn't working.

does the 99 read the voltage from the pcm? maybe try scanning the ecu and see what its says for battery voltage.

I have a 99 and mine was doing the same thing, sporadically. It is the alternator, I just replaced mine and it is much better now. Mine still ran at 0 volts, but I doubt it would run for very long.