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Unread 02-08-2011, 12:20 AM   #1
ErikTheRad
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1993 ZJ 
 
Join Date: May 2010
Location: Marysville
Posts: 420
60 amp "alt 2" fuse blown, couple questions

93 GC, 5.2 V8

I installed a new alternator last week and everything has been great-- battery voltage and alternator output are spot-on. This afternoon, my wife called me at work at told me she was in the Walmart parking lot and the Jeep won't start. The lights and radio come on, but when she hits the key, it just clicks and goes dead. Sounds like a bad ground or cable connection somewhere, classic symptoms. She got a jump start from a guy and the Jeep started and she was able to get home.

So I get home tonight and check it out, battery voltage is at 12.8v and alternator output voltage is at 14.2v. I find the ends of the ground cable on the battery are a bit loose and corroded, so I cut back some insulation and reconnected everything tight. Well while I was fartin' around with the ground cable, I thought I heard a faint "tick" from the fuse block right behind the battery. When I tried to start the Jeep again, it would spin over but would not start. I pulled the fuses out and found the 60 amp fuse marked "alt 2" was popped.

So, did this fuse pop from me screwing around with the ground wire? And if so, is this why the Jeep won't start? What is the likely situation here? Could there be a short someplace, or did I do it? I just want to make sure its not something else that could have caused the fuse to blow, I don't want my wife stranded again. I'll need to send her for a fuse tomorrow and talk her through the replacement procedure over the phone, I gotta work. Thanks for any advice!

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Unread 02-08-2011, 09:53 AM   #2
ZJ5point2GCL
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1998 ZJ 
 
Join Date: Oct 2009
Location: Calgary
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^^^^ hes right, the two fuses caused allot of frustration over a period of time for me, the jeep would run fine then when the electrical load got too high the fuse would blow, so i kept replacing it, the i eventually figured out there was two fuses and the other one was blown, no idea why jeep couldn't of put the two fuses near each other.

the one click and no start makes sense to a deadish battery, from the alternator not charging it.
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Unread 02-08-2011, 11:38 PM   #3
ErikTheRad
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1993 ZJ 
 
Join Date: May 2010
Location: Marysville
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The issue my wife was having in the parking lot and the issue I was having after getting it home are two completely different issues. My wife's issue was due to a bad ground on the battery, which I discovered and repaired. The issue in question is regarding the blown 60 amp "alt 2" fuse, which I think popped while I was messing around with the ground wire (not sure though). Would this prevent the engine from firing? It turns over just fine, just wouldn't fire.

After more research, it appears that this fuse would have nothing to do with the engine not firing unless the battery was depleted enough that it could no longer provide enough juice to fire the coil. But simply popping the fuse would not keep the engine from running, so my problem was elsewhere......

Apparently, while cleaning and reconnecting the negative battery cable, the small black wire on the negative post came loose and fell down beside the battery. I have no idea what this small wire does, but as soon as I discovered it and reconnected it, the engine fired right up. Anyone know what this wire goes to?
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Unread 02-09-2011, 02:48 AM   #4
5-90
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Quote:
Originally Posted by ErikTheRad View Post
93 GC, 5.2 V8

I installed a new alternator last week and everything has been great-- battery voltage and alternator output are spot-on. This afternoon, my wife called me at work at told me she was in the Walmart parking lot and the Jeep won't start. The lights and radio come on, but when she hits the key, it just clicks and goes dead. Sounds like a bad ground or cable connection somewhere, classic symptoms. She got a jump start from a guy and the Jeep started and she was able to get home.

So I get home tonight and check it out, battery voltage is at 12.8v and alternator output voltage is at 14.2v. I find the ends of the ground cable on the battery are a bit loose and corroded, so I cut back some insulation and reconnected everything tight. Well while I was fartin' around with the ground cable, I thought I heard a faint "tick" from the fuse block right behind the battery. When I tried to start the Jeep again, it would spin over but would not start. I pulled the fuses out and found the 60 amp fuse marked "alt 2" was popped.

So, did this fuse pop from me screwing around with the ground wire? And if so, is this why the Jeep won't start? What is the likely situation here? Could there be a short someplace, or did I do it? I just want to make sure its not something else that could have caused the fuse to blow, I don't want my wife stranded again. I'll need to send her for a fuse tomorrow and talk her through the replacement procedure over the phone, I gotta work. Thanks for any advice!
Any of a number of causes for the initial problem - shonky grounds topping the list.

I've never liked "ganging" fuses in parallel to "make a larger fuse" - if you need a bigger fuse, use a bigger fuse. Don't dork around with it - if you get a fuse that won't blow at the correct rating, you still have a problem.

In theory, you shouldn't blow those fuses singly - and if you manage to blow one, (!) replace both. If you blew one out, they probably came out of different bins and that would explain (potentially) the functional difference.

It would take a truly bizarre wiring fault to blow a single fuse in that circuit, if I remember the layout properly (alternator output lead to QD under the PDC, QD to a separate Buss bar in the PDC, Buss bar isolated by 2xMAXI60 fuses to rest of vehicle electrical system.)

Your alternator voltage is excellent - as long as it's stable, you've nothing to worry about there.

12.8VDC is good for your battery (nominal is 12.6VDC - or 2.1VDC/cell x 6cells,) so that's not a problem.

The "turn the key and click" is missing a symptom for effective diagnosis, however - when she turned the key to START, did all of the other power cut out? Or did stuff stay on? Often, if turning the key to START kills all power, you want to think about changing the ignition electrical switch (check your manual for location, I'm not sure where it is on the ZJ and I'm used to GM columns in the XJ/MJ...) but it's usually a fairly simple job, once you get to the wretched thing. The GM part is fairly cheap - I'm not sure about the Chrysler version. Tilt/telescoping column are important data in getting the correct part, nota bene.
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Unread 02-10-2011, 02:08 AM   #5
ErikTheRad
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1993 ZJ 
 
Join Date: May 2010
Location: Marysville
Posts: 420
Thanks for the smart reply, 5-90. As a matter of fact, yes, she did say that all of the power went out when she tried to start it. Radio off, blower off, etc, but came back on when she turned the key off and on again. It would only go black again after she tried to turn it over, which in my experience is perfectly common when the battery loses ground. No ground, no power to anything. Shes been using the Jeep for a few days now without incident so I'm crossing my fingers that the issue was indeed the battery cable.

As for the the blown fuse, it appears (without checking the fuses with a meter) that all the other fuses are intact, and the alternator output as measured at the battery seems to be, as you noted, excellent. Tomorrow evening I will check the others properly and will replace the other "alt" fuse as per your advice.
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Unread 09-28-2012, 08:42 AM   #6
zimsy
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1993 XJ Cherokee 
 
Join Date: Aug 2012
Location: Montgomery, AL
Posts: 31
5-90 is the man! I really want to splurge on a set of your cables but I want to mount it in the rear cargo area. I'm not currently running any bells or whistles and would like to know more info. Thanks for your technical input. I just checked my fuses and low and behold. Same problem. I do need to recheck my connections.
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