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Unread 12-10-2008, 07:43 PM   #1
Jstin120
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Bad Alternator?

My check gauges light has been randomly going on and off for about 8 months.

In the past month, I have noticed my headlights flickering at idle and when I turn off the Jeep, all of the accessories seem to lose a substantial amount of power. The gauges and head lights become very dim, and the fan barely works. It has no problems turning over, and I had the battery checked over the summer and it was good.

From what I understand, the TJ has a very reliable alternator, but from what I know, all the symptoms point to that. Any thoughts?

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Unread 12-11-2008, 07:11 AM   #2
Pillswoj
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Actually, your description is very much a battery on its way out.

How old is the battery?
Did you actually have it load tested?
Have you ensured that all of your connection are clean and tight?

You can use a Multi Meter to check that the main battery cables are in good shape.
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Unread 12-11-2008, 07:17 AM   #3
DaOne
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Quote:
Originally Posted by Andaloro99 View Post
My check gauges light has been randomly going on and off for about 8 months.
When this happens, one or more of your gauges will indicate a problem. If it's the charging system, it should be obvious.

That's what the check gauges warning is for...it is kind of saying "Hey you! Check your damn gauges. We have a problem here!!!".
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Unread 12-11-2008, 07:17 AM   #4
Jstin120
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I took it to a tires plus over the summer to have my tires put on, and they told me the battery was good. But, I don't know what they did if anything to test it.
I bought the jeep a year ago, and so I'm not sure how old the battery is. Will an Autozone be able to do a load test to determine?

Connections are tight.

The check gauges light indicates the battery gauge is dropping to 0. Other than the light, there is no difference in performance or anything.
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Unread 12-11-2008, 07:35 AM   #5
mdm
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Quote:
Originally Posted by Andaloro99 View Post
...Connections are tight...
It's not enough to have tight connections. They have to be clean as well.

A lot of the auto parts stores will do a free system check that will check both the battery and alternator. Sears automotive department will also.

This has been going on for eight months? Does your wife or girl friend drive this vehicle? You are lucky you haven't been stranded somewhere with a dead vehicle. I hope you have roadside assistance or friend that will rescue you because you are about to need help soon if you don't deal with the problem.
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Unread 12-11-2008, 07:40 AM   #6
Rowingfish87
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I'd say that sounds like an about-to-be dead battery...just go to any auto parts store and they will gladly load test it for you for free. (because if it is bad then they just sold you for a $65 battery)
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Unread 12-11-2008, 07:51 AM   #7
DaOne
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Quote:
Originally Posted by Andaloro99 View Post
I took it to a tires plus over the summer to have my tires put on, and they told me the battery was good. But, I don't know what they did if anything to test it.
I bought the jeep a year ago, and so I'm not sure how old the battery is. Will an Autozone be able to do a load test to determine?

Connections are tight.

The check gauges light indicates the battery gauge is dropping to 0. Other than the light, there is no difference in performance or anything.
I am leaning towards a bad, or soon to be useless battery. However, I am surprised that it hasn't given out already considering that this has been going on so long. I would definitely have it properly tested.
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Unread 12-11-2008, 08:09 AM   #8
Jstin120
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I will take it in today. Let me clarify. The dim lights and gauges have been going on for maybe a month or less... But getting progressively worse. The check gauges light has been going on since April or May. Other than the light, there were no symptoms.

By the way, I am the one that drives it. It just recently became a dd.
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Unread 12-11-2008, 09:26 AM   #9
LandoCommando
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This same scenario happened to me and it finally went about 3 weeks ago. Everything you described happened to me, when my check gauges light came on it was because my voltmeter dropped off but everything still ran fine(no noticeable drop in performance). It was indeed the alternator. It finally went when I was making a 4 hour drive and half way through my radio shut off and all of the dash gauges shut off. The thing was just barely putting out enough amps to keep the ignition system going. Pulled into an Advance on electrical fumes and had to buy a new one and do a swap right there in the parking lot. When they did their test on it the meter read it was putting out about 6 amps. great.
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Unread 12-11-2008, 09:29 AM   #10
Jerry Bransford
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My bet goes with those suggesting it's very likely your battery going out. The TJ's alternator is very reliable, few report problems with it that could actually be traced to the alternator itself. Even then, when the alternator itself is bad (rare), it's normally just full of mud which can be rinsed out with water then WD-40 to get it working again.
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Unread 12-11-2008, 09:32 AM   #11
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It's pretty easy to check the basic functionality of the alternator yourself. You just need a simple voltmeter. Test the battery leads with the engine off. Then test them again with the engine running. There should be a significant jump in volts with the engine running. I forget the exact numbers (a search should reveal them) but somewhere around 12 v off and 13.6 running.

If you don't get this change in volts then your alternator is not functioning. Although just to add something, when the alternator quits, it's very unlikely you'd be able to start the jeep more than once or twice, if at all.

Most auto parts stores will also check the alternator for you (although you'll have to pull it).
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Unread 12-11-2008, 09:41 AM   #12
Jerry Bransford
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That method works well if the battery isn't fully charged but if the battery is charged, the alternator won't really be putting much if anything out so the voltage difference would be little to none.
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Unread 12-11-2008, 09:52 AM   #13
Jstin120
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Thanks for the good input. I am going to take it in over lunch here, so I will let you know in a couple hours. When the jeep is off, the voltage gauge is very low, maybe 6?

The battery explains the dimming of lights but what about the random check gauges light for the long period of time? Can that also be traced back to the battery? When the light started going on, I had the battery checked and it was ok.
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Unread 12-11-2008, 09:53 AM   #14
Jerry Bransford
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A low battery can cause all kinds of strange problems. Based on the battery only reading 6 volts, I'd bet $$$ your battery is toast.
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Unread 12-11-2008, 11:17 AM   #15
Jstin120
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Just left autozone. They said they were pretty sure it was the alternator. They said the battery was good but it wasn't getting charged. The alternator was only kicking out 13 volts at idle instead of 14.
It has never been off road, so there shouldn't be mud or grass or anything built up in there.

Jerry, I was wrong, the gauge reads like 10 when the engine is off the the accessories are on.

Thoughts?
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