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Unread 05-13-2014, 03:48 PM   #1
Dtowncats
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Electrical issue, high voltage

The other week I went to start up my Jeep and it just clicked. I pulled the battery out and got it charged at Autozone. All was fine until today. Went out this morning to leave and it wouldnt start again. I jumped it with my car and everything seemed fine. Volt gauge was reading just under 14. Decided to check with my DMM and the battery was reading 16.5 volts and the alternator was giving a reading of 16.7-.8. What is going on here? Battery is no more than 6 months old. Not sure of age of anything else.

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Unread 05-13-2014, 08:30 PM   #2
HighLonesome
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Quote:
Originally Posted by Dtowncats View Post
What is going on here?
I doubt your DMM is a Fluke
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Unread 05-14-2014, 08:37 AM   #3
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Quote:
Originally Posted by HighLonesome

I doubt your DMM is a Fluke
This. There's no way the voltage is that high. Try another meter.
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Unread 05-14-2014, 09:28 AM   #4
big98tnzj
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If the alt actually is reading that high then your pcm more than likely has a short in the charge field. If the battery is reading that high then either the alt is overcharging and the battery is swelling and getting ready to explode or you have a bad cell in the battery and its causing all of your problems

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Unread 05-14-2014, 07:16 PM   #5
Dtowncats
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Quote:
Originally Posted by HighLonesome View Post
I doubt your DMM is a Fluke
You got me... I bought a new Klein today and both readings are 3 volts lower. 13.5 and 13.7-.8.

Now that thats taken care of, where can I start to figure out where this dead battery is coming from?
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Unread 05-14-2014, 08:05 PM   #6
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Parasitic drag or a bad connection somewhere. On my wifes car the voltage from the alternator to the battery post was losing over a volt. Her battery kept dying every 3-4 days. Turns out there was corrosion in the terminal and it was losing voltage and not charging properly. Replaced the terminal and no more problems.
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Unread 05-14-2014, 08:13 PM   #7
big98tnzj
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Our zjs are bad for the hatch or glass ajar switch to go bad and cause a drain

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Unread 05-15-2014, 06:59 AM   #8
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Here is a link that covers a flashing back hatch and parasitic drain problem. Their both linked some how (I didn't get into the science behind it), but you can get one symptom without getting the other. ??

http://www.jeepforum.com/forum/f13/f...ts-not-714931/

I will always start toubleshooting these kinds of problems with testing the battery with a hydrometer (very cheap) and all the power connections along with stress testing the battery, before heading into any drain situation.If the charging system is good and the battery's healthy, you can go on to the rest.
I didn't get the flicking light (others have). My battery went dead over night and it turned out to be the hatch glass switch. Easy fix.
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Unread 05-15-2014, 08:00 AM   #9
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Quote:
Originally Posted by Dtowncats View Post
You got me... I bought a new Klein today and both readings are 3 volts lower. 13.5 and 13.7-.8.

Now that thats taken care of, where can I start to figure out where this dead battery is coming from?
Sounds like your charging system is fine. Probably drain like the others said. If that isn't the problem it could be bad cabling. Make sure all the big grounds are ok too.

You need to disconnect the battery to get a proper voltage reading that would indicate the battery's health. The reading you took shows the voltage drop between the battery and alt, which is also useful. A big drop would be a bad cable or a corroded fuse connection. Longshot a shorted battery. You are getting .2 - .3 vdc drop. Seems a bit high but not sure what it should be. Likely not a problem.
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Unread 05-15-2014, 08:22 AM   #10
big98tnzj
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The best way to get a proper battery reading is check it with everything hooked up, then unhook the battery and let it sit for about an hour then retest it and see what it shows. If it shows any kind of a drain at all, leave it unhooked over night and retest in the morning. Ive seen brand new batteries off of the shelf when i used to work for advance auto be bad because they didnt have the right amount of electrolites in them or they were banged around after production. If your battery comes out good, start checking all of your grounds before you start digging into any kind of drain issue

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