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Old 06-19-2009, 08:04 PM   #1
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charging problem

I replaced the battery and the alterntor. The alternator seems to be putting out 14 volts, i know the regulator is in the ecm. Does anyone know how to check if it is working or not before I change the ecm. The alt and battery hgave both been checked at auto zone and were good. If any one has any ideas, please let me know. Thanks

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Old 06-19-2009, 09:18 PM   #2
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What makes you think it has a charging problem?

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Old 06-20-2009, 02:46 PM   #3
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The battery is brand new and checks out. The alt checks out good. All wiring checked ok. Fuses good. Jeep will run, but battery doesnt seem to be charging correctly. There is no draw when key is off. Test volt meter on battery reads 13.78 volts when running. The volt meter on dash reads a little to left of the 14 volt mark. No codes out of computer and no warning lights on. Wanted to know if anyone else has experienced this problem or is this a normal reading for the charging system. Also the battery temp sensor reads almost 10,000 on the ohms scale, which according to the shop manula is normal.
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Old 06-20-2009, 03:13 PM   #4
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I don't see what the problem is. And how did you test for draw when the key is off?
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Old 06-20-2009, 03:41 PM   #5
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You wait 5 to 10 min after running engine to let battery voltage settle. you thgen hook a multi meter up to battery and watch for any type of voltage drop. It is a little tedious, but it works. Also, there is a meter that you can run over wire harnesses and see if there is a short. And to your replay about being normal, battery doesnt seem to be charging fully, I replaced it last week, and went to start it the other day and it was dead.
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Old 06-20-2009, 05:20 PM   #6
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So last week it wouldn't start? You replaced the battery, but you still had the same problem?

Sorry, your method of testing for a draw is leading you astray.

To legitimately test for a draw - use a test light.
Remove one of the battery cables, put the test light between the battery post and the cable you just took off. That puts the test light in series with everything.

Test Light off? No draw - normal.

Test light faintly glowing? A small draw. May be a clock or something that runs all the time with the key off.

Test light near fully on? Something's on! Find the draw - turn off everything, remove fuses, disconnect things till the test light goes off.

To make sure you are doing it right, simply switch on the headlights or something major - the test light will come on full.

You can also use an analog voltmeter (meter type voltmeter, a digital type will lead you astray) if it reads much less than 10 volts the draw is so small don't worry about it.

Based on what's been presented so far, the charging system sounds fine. If the battery still won't start it, check the big connections, cables, and the starter. Without removing the starter, a shop can load test the battery and check starter draw.

Removing then testing the starter like some parts houses do can lead you astray - without the load on the starter, even some really bad ones will spin.
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Old 06-20-2009, 05:55 PM   #7
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The battery os brand new and load tested fine. The alternator was taken to auto zone and alos tested fine. Problem is that the battery doesnt seem to be getting a good enough charge from the alternator. Im use to seeing on a charge from the alternator a 14.5 to 14.9 charging voltage at the batery. I am only getting close to 14.
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Old 06-20-2009, 06:43 PM   #8
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Are you using the dash gauge to determine the voltage (notorious for being inaccurate) , or several separate test meters? Not all test meters are accurate - they can vary a bunch!

A fully charged battery with the "surface charge" removed will measure 12.6. to 12.8. (2.1 volts per cell.) Run the lights on for 5 minutes, engine off, let it sit 5 minutes, then measure it. That removes the surface charge and let's it "normalize."
Or - fully charge it, let it sit for at least a week, the surface charge will slowly leak off. But neither way is a decent way to tell the condition of the battery.

Are you still having starting issues, like it won't crank, or is it that it doesn't comply with what you expect? I'm simply trying to find out if it's a problem or not.
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Old 06-20-2009, 08:05 PM   #9
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The problem I am having is that the battery doesnt seem to be getting the correct charge. I replaced the battery 2 weeks ago, drove it daily, went to strart it 2 days ago, dead battery. Charged the battery again, and checked the charging system. I used 2 different testers and a multi metere...all 3 showed just about 14 volts when running. Turned on lights, blower on full to simulate a drain with engine running...volts dropped to 13.5...revved engine to 1500 rpm and volts went up to 13.78 according to multi meter. Is this normal charging for a jeep. I am use to seeing the voltage when charging at around 14.5 volts on other trucks I have owned.
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Old 06-20-2009, 08:24 PM   #10
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Take the battery back and get another one. I have seen batteries test out fine but never hold a charge. I also went with a different brand for the next battery too. BTW My mom has a chevy tahoe and it only charges at 12.5 along with sit there while running.

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