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Unread 07-28-2010, 09:59 AM   #1
wildchild
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1989 YJ Wrangler 
 
Join Date: Dec 2007
Location: Bradford Pa
Posts: 167
Need an electrical guru

I have a very strange problem with my charging system on my 89 with a 350 and GM 2 wire alternator. I have replaced 4 alteryrnators in the past week, evetime trying another part in the system, battery,engine ground strap, charging wire to the battery,you get the idea. the alt will charge for ten min or so then quit charging. I have full battery voltage to the alt on both wires so i think that is not the problem. The starter seems to be disengaging when the key is in the run position.

im kinda lost on this thing. anyone ever run into this problem before?

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Unread 07-28-2010, 10:14 AM   #2
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,806
Do you have the output fused? How long have you had the engine mod in it before the problem started to happen? You know that you are never ever suppose to load down the battery and then disconnect it while its running. It sends a shock of current through the electrical system that will blow the diode tree on the input.
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Unread 07-28-2010, 08:38 PM   #3
wildchild
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1989 YJ Wrangler 
 
Join Date: Dec 2007
Location: Bradford Pa
Posts: 167
Yes the input is fused. the fuse is good. and i know about unhooking the battery. A couple of the alternators never even charged when installed. and the mods have been done for over a year and working perfectly.
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Unread 07-28-2010, 08:40 PM   #4
wildchild
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1989 YJ Wrangler 
 
Join Date: Dec 2007
Location: Bradford Pa
Posts: 167
the output has a fuseable link in it also and is good
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Unread 07-29-2010, 08:09 AM   #5
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,806
I am stumped other than you are getting bad alternators when you replace them. I cant think of anything that would cause an alternator to blow unless you were cycling a huge load without the battery. HOw about getting the alternator from a different source.
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Unread 07-29-2010, 09:07 AM   #6
jay-h
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1989 YJ Wrangler 
 
Join Date: Dec 2006
Location: , NJ
Posts: 4,348
You said you are running the 2 wire alternator, but said above something about connecting to engine ground. That's leaving me a bit puzzled. could you clarify?

The sensor lead is best connected to the loaded part of the system. That way the alternator will somewhat compensate for minor line resistance.

Do voltage drop checks (as well as ground float checks) under full load between all major components, alternator housing, engine block battery terminals, alternator output
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Unread 07-29-2010, 10:14 AM   #7
wildchild
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1989 YJ Wrangler 
 
Join Date: Dec 2007
Location: Bradford Pa
Posts: 167
the engine ground i spoke of was a new ground strap from block to frame.did the big lead check and all were in spec. the alternators are from two different suppliers. I may have it fixed although i dont know what fixed it? my son is out test driving it now to go get parts for his Cummins.
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Unread 07-29-2010, 11:17 AM   #8
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,806
That ground is a RF ground and doesnt have any bearing on the alternator grounding. Right now do you have a ground from the engine block to chasis?
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Unread 07-29-2010, 11:27 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
Posts: 14,806
You should have a 2-6 guage ground wire from the engine to the chasis somewhere.
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