Electrical system failing after off-roading: is the alternator the culprit? - JeepForum.com
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Unread 05-21-2012, 02:25 AM   #1
papotter
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1992 YJ Wrangler 
 
Join Date: Nov 2011
Location: Honolulu, HI
Posts: 13
Electrical system failing after off-roading: is the alternator the culprit?

Aloha JeepForumers,

I took my 92 YJ out on the trail today and bounced it around quite a bit. On my way home I glanced at the voltage gage and it was pinned to the left (e.g. around 9, and it usually hangs right in the center of the gauge). When I turned the car off in the parking lot and re-started, it had a tough time turning over but did end up starting. Then, on the highway, things started getting wacky - the turn signals and windshield wipers didn't respond, the tach and speedo both dropped to zero and after a while the engine sputtered to a stall and I was left stranded on the side of the road.

My first hunch was that this points to a problem with the alternator - since the engine started up okay, the battery must be fine. But would a damaged alternator create the problems mentioned above? Would that be enough to stall the engine while it is running?

If so, any links to how to test for damaged parts or resolve this problem would be greatly appreciated. Right now my Jeep is sitting in my driveway, awaiting my repair!

Thanks in advance for your help!

Phil in Honolulu

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Unread 05-21-2012, 03:20 AM   #2
Jeepsr4me
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Join Date: Dec 2004
Posts: 5,135
Is the battery fastened tight? Could have bounced loose and shorted out. Dont know why Jeep thought to put the + nearest the fender.
But yes the ALT is what keeps the battery charged and if the battery not shorted out, is more than likely what is wrong.
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Unread 05-21-2012, 03:32 AM   #3
USMCBuckWild
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1991 YJ Wrangler 
 
Join Date: Apr 2012
Location: Sneads Ferry, NC
Posts: 976
Quote:
Originally Posted by Jeepsr4me View Post
Is the battery fastened tight? Could have bounced loose and shorted out. Dont know why Jeep thought to put the + nearest the fender.
But yes the ALT is what keeps the battery charged and if the battery not shorted out, is more than likely what is wrong.
I agree.

Check the wiring harness on the Alt, check the ground on the battery, check the fender for any sign of the battery shorting out against it.
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Unread 05-21-2012, 05:39 AM   #4
idskot
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1991 YJ Wrangler 
 
Join Date: Dec 2011
Location: Miami, Florida
Posts: 814
The easiest and best way is to take it to your nearest auto parts place that tests alts. It's a real easy and fast test and they'll tell you if your battery is being charged. (NOTE:: It doesn't mean that your alternator is busted, it just means your alternator isn't charging. A friend bought a new alt, I installed it and it still wasn't charging. After tracing wires, I found that the positive wire was ripped in two.) You can also completely remove the alternator, and take it in, and they'll test the unit itself.
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Unread 05-21-2012, 07:19 AM   #5
Gilthanas
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2001 TJ Wrangler 
 
Join Date: Mar 2012
Location: Ellwood City, Pennsylvania
Posts: 27
I'd check the battery terminals first. Then try charging the battery and seeing if it will run. If it will run enough to get to the local part store that tests take it there. Make sure they test the battery too. If you can't get it running enough to take the whole jeep. I'd pull the alt and battery and have them both tested. I've seen alot of Battery's get trashed when the alt fails. You just want to make sure you don't get boned later on if the battery is weak.
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Unread 05-21-2012, 09:20 AM   #6
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
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You can use a set of jumper cables to bridge the alternator wiring and the battery wiring to see if you have a bad cable too. It is a quick trouble shooting method.

You can take your battery and alternator to the store to be load tested but most of the issues are going to be related to not just the battery but all the wiring connections not being maintained.

You are in Hawaii and the Jeep wiring is notorious for corrosion issues. The salt air will speed things up so it is probably time to do maintenance. Get yourself a bottle of water, wire brush, sand paper, baking soda, and some grease. Disconnect the battery. Remove all the heavier guage wires from the alternator, battery and PDC, one at a time and clean them. There are good video's on youtube on what to do if you arent sure. Go to town with the baking soda and water. After you clean each one put grease on it and reattac. Grounds are just as critical so all the grounds too.
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Unread 05-21-2012, 05:47 PM   #7
papotter
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1992 YJ Wrangler 
 
Join Date: Nov 2011
Location: Honolulu, HI
Posts: 13
Thanks!!!

You guys are the best - right on! I took out the alternator and brought it into my local auto parts store and indeed, it was dead. $150 and an hour of labor later, and the electrical system is back up and running.

Very thankful to have a community of smart Jeep owners to help me figure out these issues as they arise - with a 20 year old Jeep, I'm sure you'll see more posts from me in the future.

Mahalo, guys.

Phil
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Unread 05-21-2012, 05:51 PM   #8
Que89YJ
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1989 YJ Wrangler 
 
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Location: Detroit, Michigan
Posts: 15,608
Glad you got it going. Take the time to put grease on the connections. You will be glad you did.
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alternator , electrical issue , YJ

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