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Battery won't charge: Has anyone had this issue before

ObedaTJ

TJ Enthusiast
Joined
Nov 1, 2018
Messages
164
Location
New York
Okay so about a month ago, I was driving home from work, and stopped by to get ice cream. Turned my Jeep off, it wouldn’t turn back on, acted like a dying battery. I thought it needed gas because my gas gauge also doesn’t work, I had a spare gallon in my trunk. Put it in and the Jeep started but a weepy start. I figured I should just drive home at this point, did that. On the way home the lights started dimming. The battery gauge dropped. It was a Saturday so mechanics would be closed, my dad took a look at it and said it’s the alternator. Got one from a local junkyard and it didn’t work. Got one from Autozone and it didn’t work. He then said it has to be the battery, went to Walmart replaced that too. Nothing.

The following week I take it to a mechanic and he says it’s the alternator. We replace that. Nothing, then he taps on the computer with a screw driver and says it’s the computer. Order one from Flagship which takes two weeks before I get my hands on it, replace it, the Jeep started and the batter gauge rose to 14v and seemed normal. I left it running for about 5 minutes and turned it off and back on and then the battery gauge started to drop and it seemed like it was still broken. I take it to another mechanic and he says it’s the battery terminals. I replace those. Nothing. Same thing. I then drive it back home frustrated and ready to just junk this out already.

My friend comes over and he starts playing around with the PCM wiring harness and it the battery gauges start going up and down. He is convinced that the problem is within my wiring harness. Could this be true?

Could I get a whole new engine wiring harness rather than looking for a bad wire?
 
Joined
Jun 25, 2019
Messages
49
Location
Genesee County MI
could be resistance in the wire harness but i seem to remember reading about a battery temperature sensor located under the battery that regulates charging of the battery too. im on lunch break and dont have time to research but figured id bring it up but i may be thinking of a different vehicle too.
 

Camhabib

TJ Enthusiast
Joined
Mar 30, 2019
Messages
222
Location
Boston, MA
If the power is cutting out while the car is running, it has nothing to do with the battery. Test the alternator and if it’s good, the problem lies elsewhere. Mice love to nibble on the insulation of wires, and 20 years of use can leave any connector worse for the wear. My guess is it’s something as simple as that.
 
OP
ObedaTJ

ObedaTJ

TJ Enthusiast
Joined
Nov 1, 2018
Messages
164
Location
New York
Showed my father where I thought the problem was and dropped it off at his house. He immediately got to work and started undoing the wire harness tape and black cover. He looked very carefully for spliced wires or places he thought were creating a short. He eventually found the wire and it was the dark green one. He cut the bad part off and redid it.

Everything works fine now. Jeep is back to normal. New computer, alternator and battery for really nothing lol
 

Daryl

2004 Rubicon
Supporting Member
Joined
Apr 29, 2018
Messages
1,236
Location
Earth 🌎
Showed my father where I thought the problem was and dropped it off at his house. He immediately got to work and started undoing the wire harness tape and black cover. He looked very carefully for spliced wires or places he thought were creating a short. He eventually found the wire and it was the dark green one. He cut the bad part off and redid it.

Everything works fine now. Jeep is back to normal. New computer, alternator and battery for really nothing lol
Thanks for posting the fix to your problem.
 
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Joined
Jun 25, 2019
Messages
49
Location
Genesee County MI
good to hear. its really quite interesting what a little bit of resistance in a wire can do.

several years back the neighbor was having issues with sensors and the computer controller on his skid loader after snow plowing all season and after diagnosing, i spent several hours cutting, cleaning and adhesive lined shrink tubing multiple wires in several large looms. the skidsteer was a former rental machine that must have had a shady mechanic. after initally reviewing wire diagrams we learned that alot of the harness plugs in the wiring were cut out and wires were simply butt connected then hidden with plastic wire loom.