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Old 09-02-2019, 08:02 AM
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Dying battery/hard starts

Hello. I have a 2005 TJ and am having battery charging problems. The battery that was on it was 4 months old 2 days ago I went to start it and it had just enough power to start the Jeep but only barely. While cranking I would get the clicking sound of a dead battery but it would eventually turn over and start. While running I put a volt meter on the battery and it was charging at 13.2-13.4 volts at idle and 12.2 volts with the engine off. Battery cables are clean and were tight and at no time did I ever get a check engine light and the volt meter always stayed right near the 14V mark. Yesterday morning I got in it to drive to work and once again it barely started. Got to work turned it off and tried to start it up again and it once again barely started so I pulled it to where it was on a hill so I could roll start it. When I got the chance I put a charger on it for over an hour and went to start it it fired right up. Pulled it back to where i could roll start it if I needed to and 2 hours later when I went to leave work it barely started again. Took it to AutoZone to have them check the battery and alternator. Battery tested bad and alternator regulator tested bad. They replaced the battery for free and I bought an alternator, but is it worth putting the alternator on if the voltage regulator is in the PCM?

I have read as many posts on multiple sites about this type of problem but I can't figure out where to go from here. Any help is greatly appreciated.

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Old 09-02-2019, 08:48 AM   #2
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I would get the battery load-tested before you do anything else. You might have got a bad one. I've had to return batteries in as little as a week before because there was some manufacturing defect or they just sat in inventory too long and even with a healthy charging system they wouldn't hold a charge.

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Old 09-02-2019, 09:01 AM
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I put the replacement battery in in their parking lot and the Jeep fired up no problem. But by the time I got back home it was late so I haven't been able to do any more testing with a volt meter. If the voltage regulator is going bad will it throw a check engine light or code of any kind?
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Old 09-02-2019, 09:43 AM   #4
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First see if new battery solves it


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Old 09-02-2019, 10:15 AM   #5
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What does voltmeter show when running?

At idle

At 1200 rpm

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Old 09-02-2019, 10:22 AM
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One in the dash or a DMM? I'm at work right now and I drove my other Jeep so it will be tomorrow before I can check anything. I'll report back. Thanks for the suggestions so far.
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Old 09-02-2019, 11:21 AM   #7
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One in the dash or a DMM? I'm at work right now and I drove my other Jeep so it will be tomorrow before I can check anything. I'll report back. Thanks for the suggestions so far.
Put a DVM on the battery terminals with Jeep running.

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Old 09-02-2019, 12:11 PM   #8
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Not sure I'd trust AutoZone to diagnose a voltage regulator issue. Since you have the fresh battery in it, check what voltage you have when running now.

I'd probably toss the new alternator on it you already have it.
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Old 09-02-2019, 01:17 PM   #9
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Quote:
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Not sure I'd trust AutoZone to diagnose a voltage regulator issue.
I wouldn't trust the averaging Autozone employee to diagnose anything beyond a flat tire.

12.6v between the battery posts (not the connectors) without the engine running indicates a fully charged battery.

I'd physically remove both battery connections and clean them thoroughly with a wire brush. Bad/dirty/corroded/loose battery connections can look perfectly fine to the eye. If that doesn't help take the battery to your nearest automotive battery specialty shop and require a load test be performed on the battery. Don't ask a normal auto parts store to do it as few know how to properly conduct a load test. The load must be held on the battery no less than ten seconds. Less time than that and a load test will incorrectly indicate the battery is good.
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Old 09-02-2019, 01:56 PM
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I didnt check the voltage before I got it started to come to work yesterday but when I got to work I got out my meter and measured the voltage on the posts and was only getting 10.4-10.6 volts. But I got back in it to see if it would start, it cranked and clicked a few times then finally started up. Once it was started thats when I pulled over to our garage to put it on the charger. How the heck would it start with such low voltage coming from the battery?
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Old 09-02-2019, 02:01 PM   #11
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Clean the terminals etc as suggested above.

Check all ends of the cables and grounds.

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Old 09-02-2019, 02:04 PM   #12
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He said he just got a new free battery so letís at least see if that helps or solves problem before we jump to something else


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Old 09-02-2019, 04:36 PM
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It will be a couple of days but I'll be back with what I find. Thanks again.
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Old 09-02-2019, 05:26 PM   #14
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Osmium states that his battery cables are clean and tight. He further states that he gets 13.2-13.4 volts with the engine running.

I think the 13.2-13.4 volts is a little low, but should keep the battery charged if the Jeep is driven during the day.

I'd check the grounds (remove, clean and put back with a dab of dielectric grease) and check for a parasitic draw.
With the Jeep not running, disconnect the (+) cable and measure the draw (if any) between the (+) post and the (+) cable end.
Also, check the heavy leads to the starter. Are the bolts that hold the starter to the block clean and tight? How old is the starter?

As a couple posters above suggest, Osmium might have had a bad battery and the new battery might have cured the issue.

Let us know how it goes.

Good Luck, L.M.
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Old 09-07-2019, 05:10 PM
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Finally got to work on the Jeep. I cleaned all the cable connections with sandpaper and wire brush also put some dielectric grease on them. Got everything back together and with the new battery I’m getting 12.5V with Jeep off and this is with it sitting untouched since Sunday. While running I’m getting 13.9V on both the battery posts and on the battery clamps and also from the alternator post to the battery negative. I have not installed the new alternator yet as I wanted to see if cleaning all the connections changed anything.
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Old 09-07-2019, 07:48 PM   #16
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Usually a strong charging system should be 14.4 when running. Does it increase if you rev the engine?
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Old 09-07-2019, 08:19 PM   #17
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I can't get my TJ to go above 14.0v and it's usually in the 13.6 area.

I've installed two Mopar alternators, no change. I replaced all cables.



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Old 09-07-2019, 10:06 PM   #18
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Actually, I guess I've never put a meter on mine.... Might do that tomorrow.
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Old 09-07-2019, 10:13 PM   #19
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I can't get my TJ to go above 14.0v and it's usually in the 13.6 area.

I've installed two Mopar alternators, no change. I replaced all cables.
The output voltage from the alternator depends on the state of the battery charge. The more fully charged the battery is the lower the voltage from the alternator. 13.6 sounds about right when the battery is at or nearly fully charged.
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Old 09-07-2019, 10:14 PM   #20
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The output voltage from the alternator puts out depends on the state of the battery charge. The more fully charged the battery is the lower the voltage from the alternator. 13.6 sounds about right when the battery is at or nearly fully charged.
That's what I've read multiple times in the forums.

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Old 09-07-2019, 11:33 PM
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The highest I can get the voltage to go up to is 14V while revving the engine. At this point I think it was the battery that I had at the start. Any other ideas or things to check?
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Old 09-08-2019, 12:24 AM   #22
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Originally Posted by Luckymac View Post
Osmium states that his battery cables are clean and tight. He further states that he gets 13.2-13.4 volts with the engine running.

I think the 13.2-13.4 volts is a little low, but should keep the battery charged if the Jeep is driven during the day.

I'd check the grounds (remove, clean and put back with a dab of dielectric grease) and check for a parasitic draw.
With the Jeep not running, disconnect the (+) cable and measure the draw (if any) between the (+) post and the (+) cable end.
Also, check the heavy leads to the starter. Are the bolts that hold the starter to the block clean and tight? How old is the starter?

As a couple posters above suggest, Osmium might have had a bad battery and the new battery might have cured the issue.

Let us know how it goes.

Good Luck, L.M.

I have a hunch the right question may have been asked here.
A starter on it's way over the hill can cause everything I've read here.
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Old 09-08-2019, 12:30 AM
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I’ve owned the Jeep since 2007 and I’m the second owner so as far as I know everything on it is original.

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