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Unread 09-29-2013, 02:56 PM   #1
THLL
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1991 YJ Wrangler 
 
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ZJ runs only on battery.

So check engine light came on, headlights starts to dim, battery gauge slowly going down, gauges shut off then dead. Even the battery full charged it runs until the battery dies. I got the alternator tested and its great. Battery is good too. The engine code gives me a 34. What could this possibly be??

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Unread 09-29-2013, 03:38 PM   #2
WhiteOut
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Have the battery tested. Are the grounds at the battery and alternator good?
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Unread 09-29-2013, 03:40 PM   #3
HighLonesome
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Check the alternator fuses in the PDC. Sounds like the alt and battery are disconnected.
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Unread 09-29-2013, 06:15 PM   #4
THLL
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yeah got the battery tested too and its good. Wheres the PDC? is that the fuses on the passenger door? I lost the side panel to that so anyone have a diagram?
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Unread 09-29-2013, 06:16 PM   #5
THLL
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NVM I googled it. Ill start checking all the fuses. and I cleaned off the grounds
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Unread 09-29-2013, 06:48 PM   #6
THLL
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Checked everything.. very weird. maybe is the ecu?
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Unread 09-30-2013, 08:09 AM   #7
HighLonesome
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Doubt its the PCM, but could be. At idle, check the DC voltage across the battery and then the alternator. Should be exactly the same.
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Unread 09-30-2013, 12:48 PM   #8
JohnnyZJ
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how old is the battery?
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Unread 09-30-2013, 04:50 PM   #9
HighLonesome
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Quote:
Originally Posted by JohnnyZJ View Post
how old is the battery?
If the system voltage is slowly decreasing until stall it means the alt isn't working or disconnected. He should be measuring around 13.8+ volts at both the battery and alt.
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Unread 09-30-2013, 10:32 PM   #10
rep-tile
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Check the belt tension. Maybe the belt isn't driving the alternator, just slipping through. Is it the 4.0? The belt must be VERY tight on the 4.0, about 180 lbs.
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Unread 10-01-2013, 09:31 AM   #11
JohnnyZJ
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Quote:
Originally Posted by HighLonesome View Post
If the system voltage is slowly decreasing until stall it means the alt isn't working or disconnected. He should be measuring around 13.8+ volts at both the battery and alt.
or the battery isn't holding a charge.

i've had 2 batteries tested that measured around 14. and they died right away when you put a load on em. one of them was my fancy 3 yr old Optima redtop........ lasted 3 years and 4 months...... just long enough to get out of warranty. best 300$ i ever spent................ (sarcasm and lies)


just saying don't overlook the obvious stuff first! no juice leads to battery/alt 90% of the time.
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Unread 10-01-2013, 12:09 PM   #12
HighLonesome
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Quote:
Originally Posted by JohnnyZJ View Post
or the battery isn't holding a charge.

i've had 2 batteries tested that measured around 14. and they died right away when you put a load on em. one of them was my fancy 3 yr old Optima redtop........ lasted 3 years and 4 months...... just long enough to get out of warranty. best 300$ i ever spent................ (sarcasm and lies)


just saying don't overlook the obvious stuff first! no juice leads to battery/alt 90% of the time.
no doubt...and a couple voltage measurements would tell you a lot
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Unread 10-01-2013, 03:01 PM   #13
NewHorizon
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I had to put an alternator on my 96 this morning. Yesterday I had the battery tested and it was good. Would not start this morning. I hooked my charger to it a few minutes then turned it over to boost and fired her up. Was running very rough and all the interior lights and such seemed dim.

I took the socket handle and tapped the alternator and everything brightned right up. I drove about 12 miles had it tested and it was bad. So, from that I gather an alternator may be in the process of quitting but work intermitently.
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Unread 10-02-2013, 04:19 PM   #14
JohnnyZJ
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Quote:
Originally Posted by HighLonesome View Post
no doubt...and a couple voltage measurements would tell you a lot
k thats it. lets goto this guys house and figure out why its dying lol
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