I have a 1999 Jeep cherokee sport with the inline 4.0l. Recently I noticed that after I am driving for a little bit the battery voltage drops down from just about 14 to the minimum 9 mark and the check gauge light comes on, the car seems to start up fine and it also seems to run fine. The radio and all lights still work correctly. If I turn the car off then put the key on accesory the battery voltage seems to go up to just below 14 which is fairly normal...my battery is also new within the last 2 months it was replaced it is an Interstate battery.

This has been happening every time I have driven the car the past 4 or 5 days.

Any advice or input is appreciated

Thanks

 

Start by cleaning all of the grounding points. Any of the ground points can cause our XJ's to do some strange things.

 

I cleaned the terminals on the battery and also the connections with the water/baking soda solution....What other parts are you suggesting I clean?

 

the other ground points would be at the battery to the fender, oil dip stick, rear of the head to the fire wall and at the coil. Also check and see if the starter in covered with oil. If so remove the starter and clean the connections and clean the area that the starter mounts to the bell housing. BTW, even if the look clean still clean them because they do build up a fine coat of crud that can cause a problem. Just take a piece of sand paper and make them nice and shinny.

 

Good suggestion about cleaning grounds. If that doesn't fix it, I'd try to check the voltage with another voltmeter while it is acting up. You could even get one of those little digital voltmeters that plugs into your cigarette lighter.

 

Might give the ignition key a shake next time the voltage drops and take a look at the ignition switch plug for signs of heating too.

 

What do you mean by that? I am sorry I am a total newbie here I recently acquired my XJ after wanting a jeep, I have only known German cars my whole life, I was figuring my XJ would be a walk in the park maintenance wise...

SO far it has done it every single time I have driven the car for almost the past week...of course the positive battery cable at napa would have needed a lot of modification to work...my positive cable is pretty corroded almost looks like the PO replaced the negative one.

 

XJ was engineered by a couple of cavemen. A lot of the electrical load flows directly though the ignition switch instead of outboard relays, thus the switch can run warm- or hot- and fail.
I'm wondering if yours is starting to fail and the low voltage in "RUN" but not in "ACC" is the symptom. There are no relays in the path to that voltmeter, only the ignition switch.

One way to tell if the ignition switch is part of your problem is to work the key back and forth to see if your problem goes away.
Next thing to do is examine the switch itself and the plug. They are on top of the steering column about 2/3 of the way down. Sometimes you can see where the pins are discolored or the plastic is melted.

 

Also check for a loose connection at the alternator.

 

I appreciate your multiple responses Radi...when you say work the key back and forth do you mean between acc. and switching the car on or what? Its weird the only time that the car did not throw the check gauges light lately and drop to the minimum voltage was the time after I cleaned the battery terminals with the baking soda and water mixture the one trip to my buddys house after I did that it remained at the normal 14v level and no check gauges light was thrown...but then immediately the trip home it did the usual drop...that is one of the things that prompted me to think it was something with the battery cables maybe...I could be totally wrong but it was a idea...just want my XJ to be fine again love going into the looking mudding trails this thing has gone some places that I cant believe a stock jeep ever could i love it

 

Jiggle it back and forth while the engine is running.

Your battery cables- are they in good shape? If moving them around made the problem better temporarily they'd be worth a closer look.

 

The negative one seems to be in decent shape looks like it may have been replaced by the previous owner...the positive one looks like crap and it would make sense because that is the harder one to replace...I am just having trouble finding the cable to replace it with not a ton of auto parts stores around me in a small town in CT....may have to order something

 

Had these exact symptoms and turned out to be the alternator.

 

There is a forum member who makes some pretty heavy duty cable sets:

http://www.kelleyswip.com/price.html

 

I am really starting to wonder if that is my issue....*UPDATE*

Tonight after driving the car and getting gas and turning it back on the car started with the voltage at the minimum 9 and the check gauges light was immediately on...also as I was driving home my headunit totally lost power a couple times, the gauges and lights of the interior like the climate control and speedo and everything the backlight was almost invisible and also the headlights were dim beyond belief as well as the high beams...i had to physically push my passenger side front window up as it would not go up with automatic switch and my drivers window went up on its own but barely and much slower than usual...also the airbag light was on for some reason...is this most likely an alternator issue?