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Unread 08-09-2011, 08:18 PM   #1
muddy94yj
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1994 YJ Wrangler 
 
Join Date: Aug 2011
Location: loveland, ohio
Posts: 19
over charge

i have a 94 yj and i just replaced the ecm in it and now the check engine light is on and it is over charging... it was running at 14 and now it is almost to 19 if i dont run the heater and lights..... can anyone lend me a hand....thanks

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Unread 08-09-2011, 11:03 PM   #2
deathtrap
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1993 YJ Wrangler 
 
Join Date: Jun 2011
Location: Hemet, CA.
Posts: 316
check and see what code you have. but if it wasnt over charging before you replaced the pcm you probly
got a bum one. the voltage regulator is in the pcm on these. other possiblity is a shorted to ground field wire
Hope this helped.
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Unread 08-10-2011, 07:24 AM   #3
pasinbuy
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1994 YJ Wrangler 
 
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Location: florida
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Fix it right away, in fact do not drive it or you may burn out components or blow your battery with the over charge.
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Unread 08-10-2011, 09:34 AM   #4
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
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That is no joke. You are full fielding the alternator and it is dangerous. You can boil the battery and it can explode. Do not drive it unless you totally disconnect the alternator!

You either have a bad ECU or a short in the control line from the ECU to the alternator.
Here is a link to pic of the charging system laybackman posted. Disconnect the battery and check the resistance of that wire going from the ecu to the alternator to ground and see if its shorted If it is then pull the ecu connector and see if it is still shorted.
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Unread 08-10-2011, 04:08 PM   #5
muddy94yj
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1994 YJ Wrangler 
 
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thanks for the tips..... i thought there were 2 voltage regs.... 1 in the ecm and 1 in the alternator..... i am pulling the alt and having it checked... im also going to do the tests that Que89 suggested
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Unread 08-12-2011, 08:52 AM   #6
Que89YJ
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1989 YJ Wrangler 
 
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Here is the link I should have posted.....blonde isn't a hair color...it's a state of mind.

http://www.jeepforum.com/forum/f12/c...gurus-1123014/
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Unread 08-18-2011, 06:47 PM   #7
muddy94yj
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i fixed my over charge problem.... i did a ecm voltage reg bypass and installed a external volt reg..... it works like a charm
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Unread 08-18-2011, 07:18 PM   #8
Que89YJ
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1989 YJ Wrangler 
 
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So the ecm was just grounding the alternator control? The voltage regulator was a problem on the SMEC modules that Chrysler put in the cars in the 80's. I'm glad to here it's all good now. In my testing I've seen the batteries blow apart from full fielding. Where did you get the regulator from?
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Unread 08-18-2011, 09:27 PM   #9
muddy94yj
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i got it from smyth auto parts along with the pig tail for it
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Unread 08-18-2011, 09:36 PM   #10
muddy94yj
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this is where i found out i could do it pirate4x4.com.... and this is where is got the how to http://www.thedieselgarage.com/forum...ad.php?t=58251


i dont do to much of my own car repair(untill now...lol) so i had to get the instructions on how to wire it up
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Unread 06-19-2013, 02:32 PM   #11
BIGEARS270
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1984 CJ7 
 
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I am having a overcharging problem with a 86 Cherokee with a 2.5. I have replaced the battery and the alternator with no change. Now that it is overcharging the engine will spit spuder then die. If i pull the field wire off it runs perfect. Will the above suggestions checking the resistance on the fielding wire or replacing the ECM be the same for this vehicle or is there something i am overlooking?
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Unread 06-19-2013, 04:46 PM   #12
Que89YJ
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No, your alternator is internally regulated
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Unread 06-19-2013, 09:07 PM   #13
Que89YJ
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1989 YJ Wrangler 
 
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If you are overcharging you need to replace the alternator. Look up the cs-144 mod. It is the same thing for you with an early 4.0 with a renix controller.
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Unread 06-19-2013, 09:44 PM   #14
Duncan542
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Make sure it has a good ground on the alternator. If you have a bad ground it will keep overcharging and burn up the regulator.
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Unread 06-28-2013, 02:55 PM   #15
BIGEARS270
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I was trying to gather as much info and parts possible. The jeep belongs to my grandfather who lives more then an hour away from any parts stores up in the mountains. With all the info from the good people on this site we went through everything again and it ended up being the ecm. Runs great again!
Thanks!
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