Battery voltage too low???

I was on my way back from a 250 mile trip and when I was almost home the battery gauge went down to 9 volts and wont budge. I've killed my old battery a few times so I just replaced that and the alternater is about a year old. When I first start the heep the volts only go up to 12 for a few minutes then it drops down. Everything still works good and nothing is fading or anything like that. I cleaned the ground to the battery but nothing helped. One more thing even with the key just turned to the onn position without it running the new battery wont put out more than 12 volts. Any help would be great as this is my DD

Are you using the dash gauge for reference?

Take it to autozone, or better yet, use a volt meter on the terminals themselves to get a more accurate reading. Could be your gauge is just screwy.

You really can't trust the in dash volt gage. First step is to check it with a volt meter.

yeah I'm at work right now so I'll have to wait till I get home the gauge could be bad as it happened yesterday evening and it has started and ran a couple times since then with no faults

well on the way home the radio started to go in and out and the battery was about to die but I made it home and shut it off then tried to start it again and no go I have it hooked up to the charger and it seems like the alternator is shot I hooked up the voltmeter to the battery and it was around 11 volts I hooked up to the positive on the alternator and and ground with all the accessories on a/c highbeams fogs and the voltage would drop consistantly.

The voltage regulator is controlled by the ECM....
Might want to check all the grounds and verify the fusible link is not blown... The fusible link is the green wire going from the alternator to the fuse block terminal....

I yanked the alternator out and where the vents are on the back side it looked like they got hit by something and bent. Now part of the case was touching the inside of the alternator so I'm hoping that that was creating a short and its a quick fix. I will check that link but I'm gonna try to get the alternator tested before I get rid of it. The thing that sux is that I got it new on june 9th 2006 so if there was a warranty its probably expired

Well I took the alternator to 2 places and it tested good at both of them so now I am at a loss for what could be causing this. The jeep will die now even with a new battery and a good alternator. The next thing that I would have to check would be the ECM I guess cause it has the voltage regulator built in to it. It sux cause it looks like a new ECM is around $400.00

Check the fusible link wire....
IF it is blown... the alternator is NOT supplying the vehicle.
You are running off the battery.

I figured I post the fix since its up and running. Turns out one of the bolts on the alternator was about to break off. The bolt that was about to break was part of the connector that has 4 leads coming off of it and one of the 2 center ones was not in contact all the time. They took it apart fixed that piece for $25 and all is good. He told me that the middle 2 connections turn it on and off. Either way its fixed and running great nnow thanks for all the help