My 1999 Jeep Cherokee Sport 4.0L straight 6 lately the battery gauge drops all the way down to 9. I went and took my Jeep to AutoZone and had my alternator tested but not sure if they did it right because the guy tested by connecting to the battery. I thought he would had to directly connect to alternator and not the battery but he said the alternator was good so he didn't know what it is, after this I drove it for a while then it continued the gauge to come on. Yesterday I just got a new battery because I started thinking if it was the battery going bad. Before I got the new battery I had them test the one I had before and they said my battery was real low and that it was bad so that's when I got a new one. It was fine for one day now the battery gauge drops again. Help me!

Also I put new battery terminals and redid the ground wire by cutting and rewire it back into the terminal

 

sound like an alternator to me

 

Yup. Alternator. Good job being proactive and getting a new battery, but you need a new alternator or else the same thing will happen to the new battery and your car will switch off while driving. Not dangerously but it can get you stranded.

 

couldn't steering wheel lock up? If so than yea, dangerous

 

No that will be fine. Power steering will be off but as long as you're moving it will steer fine. Ever push a car in neutral with the engine off? Same concept.

 

Check your belt tension. a slipping belt will cause your volts to drop because the alternator isnt getting the RPMs it needs. Better to be safe and take the alternator off and replace it. I have seen alternators bench tested that would not produce 14.7 volts. Look up the 136 amp alternator swap from a durango or Grand Chee.

 

Thanks everyone I'm going to take the alternator off and take it in to get check other then the first time I went to go get it checked with it still on my Jeep.

 

Yes my belt tension is good I just recently put a new water pump and fan clutch last month. Plus when I went to AutoZone they said the belt was good.

 

Check the battery temp sensor as well...I'd check that before ripping the alt out...

 

**Also I forgot to mention that the belt is new to when I replaced the water pump and fan clutch**

 

I'll check that out too, thanks

 

I took the alternator off and took it to AutoZone and they tested it twice and both were good. So the alternator is good. They say they believe it's my computer in the Jeep. What you guys think?

 

I think taking diagnostic advice from a counter jockey is ill-advised. Check all wiring, fuses, even take your alt to a different shop for testing before you go jumping to conclusions. Could it be your computer? Sure. But I'd be double and triple checking everything before you buy another pcm.

 

Yeah I'll definitely do that because for a new one @ AutoZone it's $326 w/ core of $77

 

...and that's for a re-manufactured unit. Proper diagnostics will help you here. Do you have a multimeter? Start off inspecting the harness, checking for opens and shorts, and that it's connected properly, make sure your temp sensor is good, check the wiring there, as well as the connectors, terminals, etc...if you can, get a known good alt, and swap it in, see what happens...even if you buy a new alt, it's a damn sight cheaper than a new computer...

Get a FSM and a multimeter if you don't have them already, two inexpensive tools that will be an immense help to you.