Crockasaurus2

So for a while I would be driving My 2000 xj 4.0 and the tacometer would drop and my car would shut off, I would go to nuetral and start it back up. then I went to auto zone and the guy giggled some **** and then that stoppped happening but the voltage gauge would drop with in secounds and up to a minute after starting. That also happened when the jeep just died randomly. But today I was driving and all my gauges went nut and then my jeep just got slower and slower and when i pulled to the side of the road it truned off. I tried to start it but it doesnt turn over it just clicks. My radio and ac fan wouldn't work and my wipers were slow. I got my mom to tow me home with our truck and i check the battery and it was at 9v Its a new battery its barely one year old. I checked the connections and nothing was corroded.

CR-Snow

Alternator most likely dead. The voltage dropping and then spiking could be bad grounds. Mine used to randomly spike all the way up. Made myself some battery cables and got some good terminals and that fixed it. But the slow shut off and crazy gauges you described sound like dead alternator.