what could have caused this?

have already posted this in JU but there are some rather clever minds in here also.Anyway.....Before this happened every thing was fine....But this past mon morn as I was driving to work I did notice that the gauge for the charging system was on the line just above the red mark. Jeep still ran with only the radio on and did get me to work just fine. Now it also started fine when leaving work to go home and only when i turned on the lights did the gauge start to drop down into the red and did drop untill with luck made it home but as I was pulling into the driveway it began to sputter and quit. So I put a charge on it for a couple of hours (12 amp-6 volt) it was dark so couldn't do much more. The next morning It started but was in the same place (gauge) made it to work fine ...But when came time to leave hade to jump off when started went to same place on gauge but this time it would not keep running even with no accessories on at all and had to jump it off a couple of times to even get home. Now heres where it gets wierd yesterday I pull bettery to check it and find the water level is a LITTLE low so I fill it to the right level put slow charge on it all day. Later that day put dialetic (sp?) grease on the 4 fuses/relays or whatever you call those black boxes just above the ign coil. Also put grease on the starter relay (silver relay next to the 4 boxes). Put the battery back in start it up and now it hold a charge at the 14 volt mark (on gauge) even with lights,heater,and radio on at the same time. checked with a voltmeter and got 12.37 with key off and 14.34 with jeep running now. Sorry forgot this is on a 90 XJ auto 4X4 with I-6 4.0 no winch,no fog lights or anyother acc that could overload the system. Any ideas what could have caused this?. Incase it happens again so I can have an idea of what to fix it once and for all. TIA for any responses. Oh and sorry so page is so long
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1990 XJ with auto,4x4 no mods yet but working on it, But a stock XJ is better than no XJ at all.

I leaning toward a toasted alt. It may work fine when it is cool but quickly takes a dump when it gets a little warm. I'm going to say that your batt. if fine (for now) since it got you to work and back that day. However the missing water may be from discharging it. If you discharge that battery like that to many more times it will be a useless lead paperweight. The whole charging system has to work properly or parts start to fail. A bad batt. will overwork and destroy an alt. a bad alt. will cause you to discharge the batt. too deeply too many times and will kill that also. To be on the safe side I would replace both hell you can get them tested before you decide to get new ones.

oops.

You could've just had a bad connection at the battery. It's not always something difficult.

dirt714 said:

You could've just had a bad connection at the battery. It's not always something difficult.

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yup, clean the termials off with a mix of baking soda and water in a paste form and let it soak for 4 min or so then rins off, apply grease to the connections.

I don't think it was likely the relays, so I'm going with bad battery connections, and they like cleaning and grease, so when you cleaned and greased, you fixed it. Another possibility might be bad alternator brushes, but that would not have responded to a cleaning. When the brushes get worn the problem can sometimes come and go for a while before it stays, so keep an eye out. If it doesn't come back soon, it's probably no problem at all.

problem is the batt cables were new (pos and neg)and there was no corrosion on them.i'm kinda leaning on the alt is going in and out, prob is if it is working when having it tested will it show that it is bad or not?. Rather not have to but new one if not needed. I'll check it out anyways. Thanks for all replies.

may have found the prob

Ok after pulling the batt and batt tray started to pull the electrical plug from back of alt and found the yellow wire almost torn in two, Guessing this could cause alt to act the way it did? when going around corners it would cause the gauge to jump up and down?..