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Unread 06-27-2012, 12:35 PM   #1
Maxoverload
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1994 XJ Cherokee 
 
Join Date: Mar 2011
Location: N.M.B. - S.C., S.C.
Posts: 12
crazy charging system

My 94 xj , has been having fits , I just cant get the same symptoms long enough to know what needs fixing , while the ambient temps were in the high 90's here recently , thats always when things start to go wrong , I get run-away engine temps , then a check engine light right after the volt meter drops to approx 11/12 volts ..... then on a fresh start up on the next day , alts putting out 15/16 volts until engine gets warm and then failure shut down of alt symptoms reappear .... this xj just turned 71k on the odo . its got a new 700 Ah battery and cables , fuses all are good , corrosion is minimal for an almost 18 yo vehicle , I have never had it off road except to the grassy camp areas , for a jeep it leads a leisurely life ...... Oh , question also , while checking systems , under the dash just a few inches to left of center of the steering column , is what looks like a old , distributor condenser , to say it was a warm would be an understatement , you could not certainly hold it in your hand , for more than a few seconds ..... anyone know what it is or it is for ??? , anyone have a diagram of the under dash fuse box ??? I don't have an owners manual , never did . update : door sticker says 4-95 production , I have always treated it as a 94


Last edited by Maxoverload; 09-15-2012 at 08:34 PM..
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Unread 06-27-2012, 07:51 PM   #2
chiefbill1959
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1996 XJ Cherokee 
 
Join Date: Nov 2010
Location: Monticello, Ky
Posts: 361
Try pulling the codes for the CEL, check all your grounds. Your grounds can cause all kinds of problems. That is a starting point and then report back. Good luck.
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86 XJ, 3 in. RC, bb rear pack, 3.4 L engine
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Unread 09-14-2012, 01:02 PM   #3
Maxoverload
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1994 XJ Cherokee 
 
Join Date: Mar 2011
Location: N.M.B. - S.C., S.C.
Posts: 12
errant electrical

have disassembled and cleaned all grounds , found 4 , currently only code is code 41 , (12-41-55) , replaced alternator , removed battery tray after removing battery for a remote charge , terminals are clean , while battery was out found a frayed wire covering , passing between fender well and battery box , it continued forward thru hole in radiator support , towards headlight , disappearing into covering , this wire was green , with discolored , orange , yellow or red stripe , there is also a brown wire along side it that has a female spade end that comes from the same radiator support hole that attaches to nothing. Anytime under hood temps get to higher operating temps I loose alt charge , ( if I leave running with outside ambient temp of around 80') and up , it cant sit still longer than 10/15 minutes before charge fails . check engine light comes on . and is running on battery engine temp 190' , ac on aux fan running . ECU CPU ??? or are there other known issues ? update : door sticker says 4-95 birthday , i have always done as you would for a 94 .

Last edited by Maxoverload; 09-15-2012 at 08:36 PM..
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Unread 09-14-2012, 02:27 PM   #4
chiefbill1959
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1996 XJ Cherokee 
 
Join Date: Nov 2010
Location: Monticello, Ky
Posts: 361
Hey Max. If your going to hang on to it for a while you may want to invest in a FSM, factory service manual. I think I only gave between 15 and 20 bucks for a downloadable FSM for mine and it has all the info you could ever want as far as wiring and wires and where they go and of course anything else you could need to do on your Jeep. Best 20 bucks I ever spent. It does sound strange that it discharges when its warm. I'll check my FSM but mine is just a little different than yours I think because they changed some stuff in 96.
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Unread 09-14-2012, 03:30 PM   #5
Maxoverload
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Thanks Bill , once I have shut the jeep off , let it cool down , start back up , shows charge rate of approx 13.8 to 14.2 , variable , no check engine light , all systems seem fine till I go down the road , get stuck in traffic , under hood temps start to elevate , (engine temp remains 195/200 stable as long as a/c and aux fan is running ) fair amount of electrical demand on system from a/c and rad fan , daytime , 'no lights/lamps' , then without warning , sometimes at idle , sometimes doing 25 mph , check engine comes on , voltage drops , to whatever is in the battery , so I am running on battery . till I shut down let cool off , If I keep going , runs till systems fail from lack of battery power . 4-95 birthday , production date.

Last edited by Maxoverload; 09-15-2012 at 08:40 PM..
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Unread 09-14-2012, 04:53 PM   #6
Programbo
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1994 XJ Cherokee 
 
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Sounds odd. After dinner I will break out the wiring diagram and see if anything in the charging circuit share a common pathway or ground with any of the temp sensors.
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Unread 09-14-2012, 09:44 PM   #7
Maxoverload
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Ok getting to know the system here , have run out or reply space , wish I had known the limits earlier , Chiefbill , I will connect with you thru an easier format , Dont know how or what i am doing wrong here , my edit button will not let me remove some non essential text or comments , I cant even respond to a few sellers , alas all is not lost I will just have to keep editing and adding to the last post of mine while reading the others , regards all Leo ........... programbo , have you had a chance ? possibly spotted anything ambient temp related ? some electronics hate heat , others thrive on it . mobos hate it for the most part.

Last edited by Maxoverload; 09-15-2012 at 08:38 PM..
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Unread 10-04-2012, 11:12 AM   #8
Phreaq
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2000 TJ Wrangler 
 
Join Date: Mar 2008
Location: , CA
Posts: 207
Any luck with This one?
I have started getting a check engine light every morning, then by 2nd or 3rd start (very short time off between shut off and 2nd start), it's gone.
I was thinking my alt is going out before this, due to the drop of charging voltage in high ambient temps.
codes: 12 41 55

I have a 91 sport 2wd
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Unread 10-04-2012, 11:30 PM   #9
DullesJeep
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1995 XJ Cherokee 
 
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Location: Dulles, VA
Posts: 235
If this situation was the other way around I'd be almost willing to go with possible bad capacitors on the ECU. A bit of previous experience bias speaking here so take it for what it's worth but...

Last summer/fall/early winter I started having odd problems where the fuel pump wouldn't prime with the key in the on position for a few minutes, longer depending on how cold ambient temps were.
Long story short, I forget how I stumbled upon it, but the capacitors on the ECU (there's only 3 of them) can fail, more or less causing issues that appear very much like electrical problems.
Never had a problem in higher ambient temps, but I can see how it could be the issue. There's no real way to test for a bad capacitor (well, I'm sure there is with a volt meter and the like) other than to visually inspect them. Mine were obviously blown apart: they looked much like an alkaline battery does after it's been left in a remote for too long and has leaked everywhere. They were deformed, one even had brown goo oozing from the end. The good news is, for $6 in parts at radio shack you can replace them and save yourself a few hundred bucks compared to the alternative of buying a re manufactured ECU or taking your chances with a JY find.

Not sure if this is relevant to any of the issues folks are having here but if you've exhausted all other routes of diagnosing the issues, it'll only take but a minute to pop the ECU out of it's case and have a peek at the capacitors.
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Unread 10-05-2012, 09:33 AM   #10
Phreaq
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Thanks for the heads up. I have read a little bit pointing to the ecu. I have a few more things to check before I put it down (car down is a shop term for not driveible) and pull apart the ECU.
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Unread 10-05-2012, 08:50 PM   #11
DullesJeep
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Quote:
Originally Posted by Phreaq View Post
Thanks for the heads up. I have read a little bit pointing to the ecu. I have a few more things to check before I put it down (car down is a shop term for not driveible) and pull apart the ECU.
If you do go to pull apart the ECU, like I said, takes a couple of minutes. Unbolt the ECU from the engine bay/fender, unbolt the connector for the pins, pry the little clips apart, and behold: braiiiinnnsss.

Here's mine after the brain surgery. Got a little happy with the RTV sealant.
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Unread 11-30-2012, 11:34 PM   #12
Maxoverload
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1994 XJ Cherokee 
 
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Posts: 12
typically , the diode trio handles the output from the alt , the more demand the more power allowed to be generated , the a/c clutch field draws a bunch , just consider the fuse for the a/c , or in comparison the fuse for fan , is not as large a draw , alt output demand is not as large just for fan than fan and a/c , at idle some things seem fine , even at bench test speeds at the auto parts store , it took me countless weeks to find the problems with an accessory loaded 89 ,ford Granada Years ago , on one Very Dark Overcast Unlit rural highway (N.J. turnpike) No other cars around me , I was shocked to find ( was overly dangerous) the faster I went (over 60) the dimmer my headlights were getting , I Thought i was going crazy or overly tired , Had the stereo going , a/c on , and was running out of power . finally getting home car still would occasionally end up with a low battery , but not consistently , if I had a moderate cruise day , did not load the charge system down , it would generate just enough to put some charge back in the battery , if it had been a highway day short trips and use of a/c , I would end up with what seemed like a bad connection or low battery ...... needless to say I did eventually have the alt removed and diode tests done , 1 of 3 was bad . made me crazy for 2 months . a bench test may not always be a true indicator , even on a replacement part . I am currently chasing a similar problem in my 95 xj , this weekend before spending $100+ I will open the ecm and look at the capacitors as suggested by another member here , as I am on a replacement alt , caused by the same lack of charge problem , the only difference being , upon opening my old alt , the brushes were shot , No need to put it back and have them hang up away from the armature , as for the ecm , they can be compared to light bulbs , they do burn out , fords control modules of the late 70's and 80s , are a prime example , However some jeeps have wiring issues due to both chaff and heat exposed to as well as relays and other malady's , if any you find where , let me know as I will you . ( do a web search on " Defective Samsung TV capacitors " , 7.5 million of em , usually showing up in tv sets , and see what corporate piracy did to one of those foreign country companys attempting to copy another companys cap. formula , some tv sets have even caught fire , and i dont think anyone can say , those same caps did/didnot not make their way into other electronics . ....... out. Thanks , to you DullesJeep , Great Idea , you cleared a few cob webs outa my head .
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