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Unread 05-04-2010, 03:27 PM   #1
gallaghergoff
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Battery Gauge and check gauges light.. once again

ok, so posted this a few days ago and solved my problem.. or so i thought.

after checking the batter and the alternator and tightening a loose ground connection the jeep ran great. the batter stopped dropping to 9 volts on the gauge so i was happy. then it started again, so i took it to the jeep dealership and they told me that my water pump was bad and that it was slowly dripping coolant on the belt causing it to slip and thus was the cause of my alternator not charging my battery. they wanted $490 to replace it and i told them no way. took it home did it myself also replaced the thermostat and it seem fine once again. let the gf drive it to work the last few days cause she has a much shorter commute then i do and she says the light never came on.. i get in it today and its on right as i start it. got my meter out and while running the batter is at 11.9v so i know its loosing its charge just not sure why.


any ideas??

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Unread 05-04-2010, 08:14 PM   #2
Rob K
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Sounds like you already checked the charging circuit connections. There's a good chance the brushes are warn out in the alternator. When mine were starting to go bad the charging circuit would work fine, but about once every two weeks I would get charging circuit light and code. It would always be good when I got out and checked it at the battery. Had warning lights at the time. Finally after two months more of ware on the brushes and a few more failures I was able to read a low voltage at the battery.
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Unread 05-06-2010, 12:00 AM   #3
Rob K
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Just realized you said you had 11.9 volts at the battery when the vehicle was running. You should measure from 13 to 14 volts or maybe a little higher when the charging circuit is working correctly. With the vehicle not running you should measure over 12 volts for a fully charged battery. If all your connections are clean and solid I'd suspect the alternator. If you've been running it a number of years it could be that the brushes are warn enough that they fail to make contact once in a while. As they ware they will lose contact and fail more often. If you are so inclined and the alternator is bolted together, you can open it up and look.

Last edited by Rob K; 05-06-2010 at 12:17 AM..
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Unread 05-06-2010, 12:15 AM   #4
Rob K
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Just realized you said you had 11.9 volts at the battery when the vehicle was running. You should measure from 13 to 14 volts or maybe a little higher when the charging circuit is working correctly. With the vehicle not running you should measure over 12 volts for a fully charged battery. If all your connections are clean and solid I'd suspect the alternator. If you've been running it a number of years it could be that the brushes are warn enough that they fail to make contact once in a while. As they ware they will lose contact and fail more often. If you are so inclined and the alternator is bolted together, you can open it up and look.
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Unread 05-06-2010, 10:05 AM   #5
tjwalker
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Primary suspect is definitely the alternator. Secondary suspect would be the computer which contains the voltage regulator.
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Unread 05-08-2010, 04:21 PM   #6
gallaghergoff
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i took the jeep in to autozone and they said that it had 0 volt output so it wasn't charging at all. took the alternator off then took that in and they told me that was fine. then when it is cold out (like in the early morning or late at night) it seems to work just fine but when it gets warmed up that is when the gauge takes a dump. i tightened the serpentine belt so i just cant figure it out lol.
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Unread 05-08-2010, 06:56 PM   #7
Rob K
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I've been told that they can't test for warn brushes in the alternator. It may have been working at the time for them. Did they look at the brushes? How many miles on your alternator? When mine failed it would work fine for a while and fail once in a while. If yours is bolted together it's easy enough to take the cover off and look. Tjwalker says it could be the voltage regulator. I'm not sure where it is. I think mines molded into the cable and it bolts on to the alternator.
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Unread 05-09-2010, 07:27 AM   #8
gallaghergoff
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the voltage regulator on a jeep is on the pcm.. lol so its about 250 i think. i guess ill be taking the alternator off again to check it, rather it be that over the pcm. got about 170k miles on the jeep. thing keeps chugging along and this is really the only major problem ive had so im still lucky in that aspect.
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Unread 05-09-2010, 09:21 AM   #9
Rob K
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So the voltage regulator is in the PCM. They could make things easier for us. Every vehicle I owned it has been part of the alternator. FYI the brushes were warn out on mine at 150k miles.
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