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tuckholladay
October 5th, 2017, 10:03
My '99 starts and runs fine, but after a few hours of driving the check gauges light comes on and the battery charge gauge drops to zero. It never dies, but I haven't really pushed it.

I tried to take off the gauge panel and clean the connections, but it didn't work. I was wondering if anyone had any other suggestions for things to check before I change out the whole alternator.

Tim_MN
October 5th, 2017, 10:29
If the gauge drops, it is likely the alternator is failing, usually the brushes are worn out. You can install new brushes for less than a rebuilt.

When the gauge drops, pull over and stop the engine, tap gently on the alternator and re-start the engine. If the voltage returns to normal, the brushes are probably worn.

tuckholladay
October 5th, 2017, 16:00
If the gauge drops, it is likely the alternator is failing, usually the brushes are worn out. You can install new brushes for less than a rebuilt.



When the gauge drops, pull over and stop the engine, tap gently on the alternator and re-start the engine. If the voltage returns to normal, the brushes are probably worn.




Thanks. It just happened. I tapped on the alternator with a ratchet and it was gone when I turned the car back on.


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smac999
October 6th, 2017, 02:38
If the gauge is dropping from 14v to 0v. And it's still running. You have a gauge issue. Measure the battery with a volt meter when this happens. It's probably still over 13v

If it's droping from 14v to 12v. Then it's an alt issue

tuckholladay
October 6th, 2017, 06:51
If the gauge is dropping from 14v to 0v. And it's still running. You have a gauge issue. Measure the battery with a volt meter when this happens. It's probably still over 13v

If it's droping from 14v to 12v. Then it's an alt issue



It drops to 0 and still runs fine. I've probably driven 30min home from work like that and it was fine the whole way.

I took the gauge panel off and cleaned the connections. That didn't fix it.

Other people were saying maybe it's a dirty ground wire.

I did take it to the parts store and have them check the battery and alternator when the gauge went down and they said it was the alternator.

It runs but I don't want to get stranded somewhere weird.


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Tim_MN
October 6th, 2017, 14:12
While you had the alternator out, did you inspect the brushes and slip ring ? If there was a problem with the wire connections, and/or grounds, the dashboard gauge would show 19 volts.

tuckholladay
October 25th, 2017, 15:46
Still trying to diagnose this. I changed the belt and there was some very uneven wear. I showed the people at the parts store and they said one of the pulleys it probably messed up. I played with them all by hand and they seem fine. The alternator pulley was the only one a little harder to turn by hand than the others. Is that normal or could that be an issue?


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RCP Phx
October 25th, 2017, 16:21
The harmonic balancers have a tendency to "walk off"!!!

Green XJ Jeep
October 25th, 2017, 18:01
Thanks. It just happened. I tapped on the alternator with a ratchet and it was gone when I turned the car back on.


I did take it to the parts store and have them check the battery and alternator when the gauge went down and they said it was the alternator.


The alternator pulley was the only one a little harder to turn by hand than the others.

Going out on a limb here and am going to say its the alternator

You can also take the alternator off and go to the parts store and they can test it on a machine

BenWheelin
October 26th, 2017, 08:03
The harmonic balancers have a tendency to "walk off"!!!

You know you're familiar with the 4.0 when you mark every one you use so you can tell this is happening before it comes off. One of the first things I do is to mark across the rubber with a bright yellow paint pen so I can tell when it shifts.

OP, brushes are less than $20, install in minutes, and you get to keep your great factory stuff instead of trading it all for a fraction of the value in some new POS from the parts store.

A simple search for alternator and starter parts yields the place I've used for years.

comanche91
October 26th, 2017, 09:24
I get alt brushes, bearings, etc. HERE (https://www.aspwholesale.com/index.php). Quick shipping and decent pricing.

comanche91
October 26th, 2017, 09:26
OP, brushes are less than $20, install in minutes, and you get to keep your great factory stuff instead of trading it all for a fraction of the value in some new POS from the parts store.

^^ This. I get alt brushes, bearings, etc. HERE (https://www.aspwholesale.com/index.php). Quick shipping and decent pricing.