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Unread 04-18-2010, 05:37 PM   #1
minnbowhunter
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1994 YJ Wrangler 
 
Join Date: Mar 2010
Location: Minn
Posts: 69
alternator overcharging?

I got this YJ after it had been sitting a year. The alt was rusted and froze tight. I get it freed up and it was charging good, too good I think. The needle on the volt gauge was almost into the red zone. Maybe 16 volts or so. I decided the old alt. was not to be trusted after being froze up, and put on a new one. The gauge is still showing the same 16 volts. I turned the key to the "on" position and it shows just over 12 v. if I turn on the lights I can see a small drop on the needle, so I think the gauge is working ok. I checked the battery connections and the electrolyte level in the battery. Everything looks good there. It runs and starts fine. What do you guys think? Am I worrying about nothing? Dead cell in the battery maybe?

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Unread 04-18-2010, 05:54 PM   #2
msprooch
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1995 YJ Wrangler 
 
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Location: Kokomo, IN
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Its probably not the battery. I would say a bad gauge. Do you have a volt meter? You can get one at harbor freight for pretty cheap if you don't. Measure across the battery when the jeep is running.
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Unread 04-18-2010, 06:02 PM   #3
moonshinefuel
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1995 YJ Wrangler 
 
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My gauge has been going into the red zone for years. Turn the lights or heater fan on and it drops down just under the red zone. Not always like that, but it is a lot of the time.
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Unread 04-18-2010, 06:06 PM   #4
Larry93
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The jeeps ECM controls the rotor field on your alternator. As long as you installed it correctly, the voltage output is most likely in spec. Check with a multimeter while running.
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Unread 04-18-2010, 06:39 PM   #5
moonshinefuel
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My gauge has been going into the red zone for years. Turn the lights or heater fan on and it drops down just under the red zone. Not always like that, but it is a lot of the time. Not sure why, just know it does it.
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Unread 04-19-2010, 08:07 AM   #6
YJhobby
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1993 YJ Wrangler 
 
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16v is a little high... 14v is typical for a charging system. Sounds to me like the gauge is working properly, and its the voltage regulator/overvoltage relay that's out of adjustment.

Course I work on airplanes, and we have the ability to adjust this stuff... I dunno on Jeeps? They may not have those parts I mentioned. Sometimes those regulators are built into the alternator, so potentially swapping the Alt could help.


EDIT: Sorry... I missed Larry93's post. I agree with that statement.
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Unread 06-04-2010, 10:12 AM   #7
cont7
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Sorry to bump an old thread, but i have the same problem at this time, i have a 95 YJ 2.5

I tested with the voltmeter and it shows 15.3 Any suggestions?

Thanks!
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Unread 06-07-2010, 10:40 AM   #8
cont7
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It's my again. I was told that an external voltage regulator would help. has anyone done it?
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Unread 06-07-2010, 11:01 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
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N o external voltage regulator. Your target is 14.5 so 15 is just a little high. See what voltage reading you have again. Fisrt ignition on, then engine running, and then turn all the lights wipers blower etc. on and read it again.
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Unread 06-07-2010, 11:45 AM   #10
cont7
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with all the lights, radio and the heater on, it still reads 15.3

When ignition is on, it reads 12.3.

so, it's a no for the external regulator?
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Unread 06-07-2010, 12:37 PM   #11
Que89YJ
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Thats a no. You will cause a bunch of grief for yourself. Your charge isn't in full field. You would be putting out 18Vdc. You have a high load the controller is trying to compensate for. Try leaving everything off, start your Jeep, disconnect the battery and read the voltage. Your battery could be an issue.
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Unread 06-07-2010, 12:40 PM   #12
cont7
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If i disconnect the battery while the engine is running, won't it cause a failure to the ECM?
The battery that i have on use it's an optima red top, i might swap it to see how it behaves.

Also, i was wondering, I installed some HID's, they are not affecting the voltage, or can they?
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Unread 06-07-2010, 12:49 PM   #13
Que89YJ
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1989 YJ Wrangler 
 
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No, the battery disconnect shouldnt be an issue unless you load down the Jeep then you disconnect it afterwards, thats called a load dump. Turn off the Jeep before you reconnect. No, the HID lights are not on so they shouldnt load down anything. The optima red top is a good battery but you need to try the obvious first. Like I said though 15.3 is not that high. You are only a few 10ths of a volt high on you output.

Last edited by Que89YJ; 06-07-2010 at 01:28 PM..
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Unread 06-07-2010, 01:06 PM   #14
cont7
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let me give it a shot then. Thanks!
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Unread 06-07-2010, 01:39 PM   #15
idaholtby
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Quote:
Originally Posted by cont7 View Post
let me give it a shot then. Thanks!
If this was not already discussed, your '95 is externally regulated. Therefor the performance of this regulation is hugely impacted by the condition of all of the battery connections. The poorer the connection, the more the alt has to ramp up it's output to compensate. For example, I experienced the same symptoms in the past. My cause was due to the battery clamps being stretched. The battery clamp was tight on the top of the post, but was oblonged and had poor contact on the bottom of the post. The end result was a high current output from the alt from it trying to compensate. Even if the battery terminal clamps look good from the top, check and ensure that they are not stretched such that only a portion of the post clamp is making contact. This may not be your issue, but it should be ruled out.
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