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Unread 03-23-2012, 04:21 PM   #1
rksnow1
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2008 JK Wrangler 
 
Join Date: Jul 2010
Location: Morrisville, PA
Posts: 171
88YJ Charging questions and help needed

Hey Jeep Pros, Need some help and suggestions here.

I have an 88 YJ 4.2 with 4.0 head conversion, nuttered, weber carb etc etc.. not that that should really matter but lots of people ask if you dont post it here first...

So issue is basically that my alternator stopped charging.. I tested the battery and alternator and both are good, even tried another good alternator and still the same issue.. showing plenty of volts but no amp output when in the Jeep. On the test machine all works correct.

What else can cause the alternator not to charge tha battery? Grounds look good, every thing worked till I pulled the motor and did the head swap. Thought it was fine after but havent driven her much since.. I may have miss connected a wire, or may just be coincidence. Im going mad trying to figure it out. I removed the radio just to make sure it wasnt a bad wire or connection there. What would you check and in what order to narrow my search....

thanks in advance.

worse case senario... Anyone make a harness from scratch? any write ups on it that you recommend?

thanks in advance

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Unread 03-24-2012, 09:42 AM   #2
rksnow1
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2008 JK Wrangler 
 
Join Date: Jul 2010
Location: Morrisville, PA
Posts: 171
bump... anyone have electrical knowledge or experienced this before?
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Unread 03-24-2012, 09:57 AM   #3
4.7stroker
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1988 YJ Wrangler 
 
Join Date: Apr 2007
Location: Rio Rancho NM
Posts: 4,299
Well lets start with the basics, there are 2 wires that connect to the back of the alt. One has a 2 pin plug the other bolts on. Are they hooked up? Also one of the wires has a 2 pin connector about 8" from the alt end is it hooked up? You will need 12vdc exciter voltage to "start" the alt are you getting that?

Why do you say your alt is not working? is it just a gauge issue or is your battery going flat?

Dwayne
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Unread 03-24-2012, 10:14 AM   #4
ashnken
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1991 YJ Wrangler 
 
Join Date: Aug 2011
Location: Bruceton Mills, WV
Posts: 48
I have a 91 that the gauge stopped working but when I put my voltmeter on the battery it shows that it is charging, Im not sure if I have a bad gauge or wiring problems.
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Unread 03-24-2012, 11:00 AM   #5
rksnow1
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2008 JK Wrangler 
 
Join Date: Jul 2010
Location: Morrisville, PA
Posts: 171
Quote:
Originally Posted by 4.7stroker View Post
Well lets start with the basics, there are 2 wires that connect to the back of the alt. One has a 2 pin plug the other bolts on. Are they hooked up? Also one of the wires has a 2 pin connector about 8" from the alt end is it hooked up? You will need 12vdc exciter voltage to "start" the alt are you getting that?

Why do you say your alt is not working? is it just a gauge issue or is your battery going flat?

Dwayne
Guage does move but stays in red, Battery isnt taking a charge and not reading amperage output from the alternator when installed in YJ. I took the alt and batterey out and had tested. All bench test fine with proper output, even tried a second known good alternator and same issue.. so thinking is the wiring.

All 3 wires on the back of the alternator are hooked up, and making a good connection. I have a single red wiire that bolts to a post connection and a white 2 prong plug with a red and brown wire in it. I dont have a 2 prong plug a few inches down the line like you mentioned, unless I am understanding wrong. This is the factory wire and wasnt altered. Basically the red wire in the plug and red wire bolted on tie back in and connect to a relay? on the firewall. The brown wire in the plug runs back in the loom and back into the firewall(Im assuming to the ignition switch or something.. havnt traced it that far) Is this brown wire the exciter wire you mentioned? Do I test while running?

Thanks again.
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