Alternator short question

[USAFREODRetired]

On our way up to the mountains for the long weekend on Friday afternoon, and made it as far as Westcliffe, CO when I get that dreaded warning that my 2018 JLUR will shut down and pull over soon. I found a garage that was still open, and one of the guys puts a multimeter to my batteries (I'm running the Genesis Offroad Dual Battery System) and is only getting 12.1V on the main and 12.5 on the secondary. I'm definitely draining through the drive, and he suggests I might have enough to turn around and make it home to the Springs. The alternator was running white-hot, unusually so. I have suspected I have a serious parasitic load but haven't had time to find it, and I can't believe that would make the alternator run so hot.

We didn't make it and about 20mi out the Jeep did start to shut down, finishing off with the loss of power steering. We get off safely and get a tow back home.

Based on the Tech's initial assessment that it was a bad alternator, I called around looking for one but turns out the 240A OEM alternators (I have the tow package) are in very short supply here in CO. Hoping to get one next week sometime.

In the meantime, I decided it would be a good time to do the "Big 3" upgrade and ordered my new cables. I pulled my alternator this AM, then proceeded to remove the main alternator to PDC cable to do the swap, and what do you know I find a nice large abraided area with a lot of exposed copper and some evidence of arcing. (BTW, anyone know exactly where the main engine block ground is located on the 3.6, can't seem to find it?)

Now I'm getting paranoid, and wondering what else I might have fried driving around with a shorted alternator. Any ideas on what I should be checking before doing anything else?

Thanks in advance!

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[58Willys]

So, did the alternator short out and burn up the wiring, or did the wiring short the alternator? Carefully check and repair wiring. Check wire for proper resistance (ohms). Also check starter and solenoid for proper function. A bad starter circuit can fry wiring or alternator. I know the JL’s have the PCR circuit, but I’m not very knowledgeable on it. There a great thread on this forum that have a ton of good info on the battery/charging system. Basically check out the entire system, and make sure everything including the batteries are good. Yes, this will take a while to do. Electrical problems are complex and time consuming. Be patient. Good luck.

 

[USAFREODRetired]

Looks like the wiring abraided over time and began shorting out the alternator. From the looks of the cable, this has been going on for a while. Kind of surprised it took this long for the problems to emerge. Other than drawing down the batteries and the occasional loss of power steering over severe jolts, nothing else was noticed and I didn't even trip a DTC. Crossing my fingers it's just going to be a cable and alternator issue.

 

[Dave928]

any chance of getting a photo of where exactly it was rubbing?

 

[USAFREODRetired]

Unfortunately, no. I couldn't identify it specifically, but somewhere behind the Genesis battery tray.

@Dave928 I see you're an Aircraft Tech. An old IA once told me you can never have enough zip ties and stand-offs on cables and hoses around a piston engine. I think he was right. This time I'm going to put an abrasion/heat sleeve along that path and zip tie the shit out of it! NO RUBBIN!

 

[58Willys]

Hopefully you can just replace the abraded piece and move on without any issues.

 

[USAFREODRetired]

Completed the "Big 3" cable upgrade and replaced the abraided cable from the alternator to the PDC, but still no joy.

Is it likely that I fried the fuse array, or is the entire PDC suspect? How do I diagnose?

Alternator is putting out 14V+ both at the device and at the bus on the PDC to body ground. When I measure voltage from the battery bus lead on the PDC to ground, only 12.1V (same as battery voltage), so it looks like it's either the fuse array or the PDC is shot (or so I hope that's all it could be...)

Any other ideas or things to check?

 

[58Willys]

Hmmm… There are a couple of very good threads with diagrams of the charging system in Batteray Talk forum.

This thread has some very good diagrams and info.
https://www.jlwranglerforums.com/forum/threads/3-6l-ess-dual-battery-consolidated-information.25377/

Start checking fuses for continuity, check/test fuse array, etc… Keep working methodically.

Electrical issues take patience and a very methodical approach. Wiring diagrams are really useful. I’m not super knowledgeable about the JL’s, but check for in line fuses in the cables; not sure the JL has them, but I seem to remember something like that on mine.

Re post this in the Battery Talk forum, some really knowledgeable folks there.

 

[m3reno]

I had a wire frayed similar to yours but mine turned out to be a mouse eating away at the outer cover

 

[USAFREODRetired]

I replaced the fuse array in the PDC, and now the entire electrical system is actually working much better than before. I think going through and methodically re-seating all of the fuses, plus going with a 1/0 AWG ground and power has just made everything work so much better. The new alternator is super stable on the voltage, much more than the old one.

If I had just done the "Big 3" upgrade when I installed the Genisis Offroad dual battery system, I probably could have avoided this entire scenario. Much higher quality cables, plus I added Design Engineering Heat Sheath along each run close the engine for extra protection for both battery and alternator lines.

Painful to go through this, but I think my electrical system is far more robust now.

 

[MtCamper]

I installed the Genesis system and unknowingly pinched the alternator wire with the Genesis battery tray. Took about 1000 miles of towing and maybe 200 drive miles for it to finally wear through the insulation. Of course by then I was over 20 miles from the highway and another 20 to my camper. Fortunately a good samaritan towed me to the highway and then gave me a ride to my camper. Got the truck and towed the Jeep back and eventually to home. Replaced the fuse array, taped up and rerouted the alternator cable and its been 2 years and lots of miles with no problems. Moral of the story is check the cable routing if you do a Genesis upgrade.

 

[Texashockeyman]

This exact situation also happened to me this morning. Stopped at a red light and just like the original poster: got the power steering warning and the car shut down. My fuse array was burned out as well.

 

[USAFREODRetired]

This exact situation also happened to me this morning. Stopped at a red light and just like the original poster: got the power steering warning and the car shut down. My fuse array was burned out as well.

Inspection of the alternator cable and grounds are now on my long road-trip checklist. Since I did the massive cable upgrade, all seems well again. I put a fiberglass fire sleeve on the section closest to the engine, and tons of zip ties. I'll be damned if I let this happen again!

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