battery gauge weirdness

I've been having a problem with my 97 XJ recently where I'll be driving and the battery gauge will drop to zero, then pop a check engine light on. It never appeared that I was actually losing voltage as I could turn the Jeep off and crank it again and the gauge would light back up to around 14v like usual. Annoying, but tolerable for awhile.

I went out the other night and it started doing the same thing, and I didn't think much of it. Ran into the store, then when I came back out, it wouldn't start. I figured that my NSS was starting to act up, but then when I couldn't get it to crank with it in neutral, I knew that something else was up. Lights, interior lights, radio, etc would all come on no problem. Cranking it a few more times, it would give up like the battery was drained and do a fast click, but the interior lights would still work. I pulled the battery and swapped it out for a new battery and so far haven't had another problem starting it up, but the battery gauge is still dropping down to zero pretty much everytime I drive it now.

I've seen a few threads with similar problems, but not really any solutions. Does anyone have any idea why this would be happening and what to check to get it solved?

:viking:

the alternator may be going out, but make sure the battery cables are clean and tight

Check all your grounds, but likely your alternator is bad. Go for a free check. When you say your gage reads zero, is it a volt gage or amp gage?

I'm guessing that it probably is the alternator, but I'll check the grounds later this week to be sure. As far as the reading, I'm talking about the gauge in the instrument cluster. That's voltage, right? I can't remember without going out and looking.

the alternator
i had the same problem...
check it ..before the batterys gone

ff4500 said:

I'm guessing that it probably is the alternator, but I'll check the grounds later this week to be sure. As far as the reading, I'm talking about the gauge in the instrument cluster. That's voltage, right? I can't remember without going out and looking.

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A lot of older American vehicles had amps -30, 0, +30, my Jeep's a 2000 and has like 10, 12, 14 volts. A car could still run good if the ammeter read 0, but 0 volts, forget it , it's dead. It can't run at all. So obviously the 0 volt reading is false, if it is volts.

Checked out all of the wires, grounds and replaced the battery terminal connectors just to be sure. Everything looked good there. Took it to Midas and had them check it running on and off all day long for free. Everything was charging how it should be. Drove to IL to pick up some tires and had no issue on the way there. On the way back, voltage meter drops off again, and it's obvious that the alternator isn't charging anymore. Drive to the next exit, pull the battery and get it home to charge back up so I can get the Jeep home again.

Guess that I need to go get a new alternator afterall.

The auto parts chains will check the alternator for free. It still could be other things, but the alternator is the likely culprit. Have it checked before you replace it.

Yeah, I already had it checked, pretty thoroughly at that. It checked out fine and worked just dandy for awhile. Then on the drive last night, it seemingly bit the dust. I'm going to replace it rather than keep going through the testing and crossing fingers stage. That way, I can narrow it down a little more if I'm still having problems.

keep us posted,, i started having the same thing happen about 2 weeks ago, so far it has not killed the battery, sunday evening the guage fell down to zero coming out of the woods,drove about 1 mile out of the woods then about 4 miles of hiway with lights & heater, when i got home & shut it off thinking it should have drained the battery.so i tried cranking & it spun right up ,no slow cranking, just like normal. i too have checked the grounds and replaced a bat. terminal, prior to the last incident.

kymtnman said:

keep us posted,, i started having the same thing happen about 2 weeks ago, so far it has not killed the battery, sunday evening the guage fell down to zero coming out of the woods,drove about 1 mile out of the woods then about 4 miles of hiway with lights & heater, when i got home & shut it off thinking it should have drained the battery.so i tried cranking & it spun right up ,no slow cranking, just like normal. i too have checked the grounds and replaced a bat. terminal, prior to the last incident.

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False reading on gage! Gage connections at cluster plug no good! Can be verified at battery with portable voltmeter. 12.5V or so with engine off, 13.5-14V running. If it doesn't go up when you start it, it's the alternator or connections. If it goes up good, it's your gage connections.

ff4500 said:

Yeah, I already had it checked, pretty thoroughly at that. It checked out fine and worked just dandy for awhile. Then on the drive last night, it seemingly bit the dust. I'm going to replace it rather than keep going through the testing and crossing fingers stage. That way, I can narrow it down a little more if I'm still having problems.

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Brand new alternators go bad too!

winterbeater said:

Brand new alternators go bad too!

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Yes they do. I had two in a row from NAPA go bad on me on my old Sentra. They just about didn't believe me when I returned the second one. Finally got an OEM one for three times the price and it worked flawlessly.

winterbeater said:

False reading on gage! Gage connections at cluster plug no good! Can be verified at battery with portable voltmeter. 12.5V or so with engine off, 13.5-14V running. If it doesn't go up when you start it, it's the alternator or connections. If it goes up good, it's your gage connections.

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The 97-01 XJs and early TJs were prone to oxidation (black specks on bus connector and instrument cluster terminals) which will cause the gauges to either lock up or drop to zero....
My Jeep has had this problem for almost 9 years.... During this time the dealer attempted to fix the problem with a TSB (cut off old bus connector and solder in new ones); didnt work for long... The terminals have been cleaned more than half a dozen times and most recently cleaned thoroughly and have dielectric grease applied to terminals... Problem still reoccurs....

When ff4500's volt meter drops to zero.... I would check the operating voltage at the battery....
A way to test the alternator charging.... would be to attach a digital volt ohm meter to the battery and then turn on the headlights, fan motor, A/C and any other vehicle equipment....
IF the voltage drops below 13.0V then the problem is either the alternator OR ECM not adjusting alternator charging rate.....
Check the terminals and connectors on the alternator to verify connectors are clean and tight.

Yup. A new alternator fixed it right up. I'll update if I still have the issue down the line.