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WTF!

Oatmeal

NAXJA Forum User
Location
Cedar City, UT
Me and a buddy went for a little trail ride (I'm in a 96 XJ, he's in his 84 Bronco) out in the Anza Borrego desert today, was warm so ran the ac all day (nice to have cold, working ac)
On the way back to pavement, stopped and aired up, drove into town and and stopped for lunch.
Afterwards on the way home, I noticed the ac fan seemed to be running kind of slow(?) then, not cold....figure shit, ac quit then, all of a sudden tach starts spazzing out then, quits followed by the speedo!
I then notice voltage gauge registers dead......WTF? So, I pull over, shut it off, check battery connections, try to start and it's almost dead, jump start and get as far up the highway as I can before fuel pump kills the battery, which it did......I should also mention had no brake lights or turn signals as well.
While waiting for the tow truck, we start checking and pulling fuses, jump start again (love those lithium ion jump starters) and it runs rough (apparently the battery recovered enough to run the pump and ignition.....barely) but, now turn signals and brake lights are on board again but, still no instruments and still not charging (charge light never came on???)
Got it home on a flat bed (AAA is best money I ever spent) pulled the battery and put it on the charger.....it's 9:30 pm by this time.
That's where I am now.....thoughts, experiences, insight?
Hans
 
Sounds like the alternator isn't charging or isn't being commanded to charge. Could just be worn brushes. What's the battery voltage with the Jeep running?
 
Start with the basics, clean and tight wire connections. Test the alternator and battery.
 
Sounds like the alternator isn't charging or isn't being commanded to charge. Could just be worn brushes. What's the battery voltage with the Jeep running?
Didn't have my multimeter with me and dash gauge didn't even register.
I've had to replace alternator before......charge light would come on before it went south and tach and speedo never wigged out like that.
I 'll look at it when I get home from work, was pretty beat when we got home last night.
Hans
 
8
Start with the basics, clean and tight wire connections. Test the alternator and battery.
Battery is fairly new and seemed to recover some when it sat for a bit, has a full charge now.
I'm hoping it's something simple like the alternator but, the whole tach/speedo thing has me worried some.
Hans
 
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The voltage regulator for the alternator is in the main computer. If the computer is shot, it could be allowing the battery to run down, and perhaps also contribute to the other problems?
 
The voltage regulator for the alternator is in the main computer. If the computer is shot, ...

It could be that, but always start with the basics, clean and tight wire connections. Testing the alternator and battery.

Once the charging system has a solid foundation, you can move on to other much less likely causes for the symptoms.
 
Sounds like the battery is taking a charge ok.

Easiest way to test the alternator is to measure the voltage at the battery clamps while the engine is running and the battery cables are properly connected ... voltage should be over 14. That would show that the alternator is at least working.

Then turn on all electrical accessories to create a significant electrical load, check the voltage while motor is running. If it stays close to 14, then the alternator is putting out a decent amperage.

If the alternator isn't working properly, it could be the alternator itself (most likely) or the voltage regulator in the computer. Pull the alt and take it to a shop to have them test it. If the alt tests ok, but isn't working in the vehicle, then start testing your computer.

We should also note that most "rebuilt" alternators suck nowadays. Autozone, Advanced Auto, Oreilly's, etc ... they all sell a lot of Chinese crap that usually takes one or two returns before you get one that's halfway decent. I just finished rebuilding my own starter motor and alternator ... using high-end Koyo Japaneses bearings and other quality components. Its really not that hard to do, and you'll know that your rebuild will work right the first time and last at least a 100k miles (unless you drag it through the mud all the time :gee:)

If you need an alternator rebuild kit, let me know. I'm a business owner, so I'm able to order from suppliers.
 
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Sounds like the battery is taking a charge ok.

Easiest way to test the alternator is to measure the voltage at the battery clamps while the engine is running and the battery cables are properly connected ... voltage should be over 14. That would show that the alternator is at least working.

Then turn on all electrical accessories to create a significant electrical load, check the voltage while motor is running. If it stays close to 14, then the alternator is putting out a decent amperage.

If the alternator isn't working properly, it could be the alternator itself (most likely) or the voltage regulator in the computer. Pull the alt and take it to a shop to have them test it. If the alt tests ok, but isn't working in the vehicle, then start testing your computer.

We should also note that most "rebuilt" alternators suck nowadays. Autozone, Advanced Auto, Oreilly's, etc ... they all sell a lot of Chinese crap that usually takes one or two returns before you get one that's halfway decent. I just finished rebuilding my own starter motor and alternator ... using high-end Koyo Japaneses bearings and other quality components. Its really not that hard to do, and you'll know that your rebuild will work right the first time and last at least a 100k miles (unless you drag it through the mud all the time :gee:)

If you need an alternator rebuild kit, let me know. I'm a business owner, so I'm able to order from suppliers.

Thank you for the offer. I've rebuilt a few alternators in my time and found that, a lot of times the brushes or rectifiers (diodes) are bad.
There's a small alternator/starter rebuild shop near me, I'll have them test it.....the auto parts counter guys don't always seem too bright.
No offense to you guys that work in that industry!
Hans
 
There's a small alternator/starter rebuild shop near me, I'll have them test it.....

That's great! That's a dying industry. You're lucky to still have one near you. They can hook you up with everything you need.

With the battery fully charged, do the other problems you described go away?
 
That's great! That's a dying industry. You're lucky to still have one near you. They can hook you up with everything you need.

With the battery fully charged, do the other problems you described go away?
I'll find out after work.....crossing my fingers. I'm usually pretty good at trouble shooting electrical issues.....need a wiring diagram.
Hans
 
Well,
Here's the latest.
Fully charged battery, fires right up, runs smooth all the instruments are working but, alternator isn't putting out.
Here's what stumps me, last time the alternator went out, the charge light (GEN) came on but, not this time.....that's what usually gets my attention so, I probably didn't notice the volt meter dropping.
I probably ran all day actually, who knows how long I'd been running that way, on the battery!

Too tired to pull the alternator tonight, you all know what a pain it is, have to remove the bracket to snake it out of there but, am I looking at a simple alternator failure or is there something more sinister lurking? And before you ask, yes the GEN light illuminates when you turn the key to IGN.

Appreciate all the input, thanks
Hans
 
I once had a 78 Camaro and on it the Gen light was in series with the 12V excitation circuit to the alternator. In other words, if Gen light bulb burned out the alternator would not charge. Don't know if yours is the same but a quick look at a wiring diagram would tell you.
 
Test the alternator to see what's what,
If it's ok then the PCM is where it's controlled from.

Hopefully it's just cleaning up some wires and not the PCM.

78 camaro, weird, those GM alternators 84-86 XJ and 87-90 XJ use as well are internally regulated, strange the charging circuit would collapse because of the bulb, but it was old school tech.


Sent from my iPhone using Tapatalk
 
Test the alternator to see what's what,
If it's ok then the PCM is where it's controlled from.

Hopefully it's just cleaning up some wires and not the PCM.

78 camaro, weird, those GM alternators 84-86 XJ and 87-90 XJ use as well are internally regulated, strange the charging circuit would collapse because of the bulb, but it was old school tech.


Sent from my iPhone using Tapatalk
Spoke to a friend that's a retired Jeep tech and he said the fact that the GEN light didn't come on could point to something other than a bad alternator....if the alternator checks ok.
He told me to check a couple of ground wires near the ignition coil and said it could in fact be the PCM.
Oh well...
Hans
 
What sucks about the 96 is it's the first obdII Cherokee and most of its parts are 96 only.
On the bright side I guess a regular scanner can tell you a bit more than the OBDI xj computers like to share


Sent from my iPhone using Tapatalk
 
Well, put a new (not remanufactured) NAPA alternator in and it's charging now.
Put my meter on the battery posts with engine running and I'm getting 13.8 volts, max turn on a/c and lights and it's down to 13.5 - 13.6
dash gauge reads much lower than my meter.....it's a Fluke so, I know it's accurate.
I'm used to my Toyotas that put out over 14 volts even with the lights, a/c, wipers......on. Should I be concerned, then again, it's always been that way(?)
The other thing that concerns me is that the GEN light never came on when the alternator was going out.
Hans
 
Well, put a new (not remanufactured) NAPA alternator in and it's charging now.
Put my meter on the battery posts with engine running and I'm getting 13.8 volts, max turn on a/c and lights and it's down to 13.5 - 13.6
dash gauge reads much lower than my meter.....it's a Fluke so, I know it's accurate.
I'm used to my Toyotas that put out over 14 volts even with the lights, a/c, wipers......on. Should I be concerned, then again, it's always been that way(?)
The other thing that concerns me is that the GEN light never came on when the alternator was going out.
Hans
Mine puts out over 14 on the dash with everything running, let me go to the shop and verify that though, you ain't lying, it's nice to have a fluke

Sent from my SM-G935V using Tapatalk
 
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