Jon Iwanyszyn

Well I had a fun night. Went out to get some things in town, as I left I noticed my voltage meter dropped to 9 or bottomed out with the check gauges light on. Hoping I might just be having a gauge issue. Yet this is what was happening before, I thought I should just take the Tahoe but went for it anyway. Came out of wally world and noticed when I first turn the Jeep on it reads 12 volts, meaning I'm running on my battery, then it bottoms out. Noticed my headlights are dimming, so I try to get home as fast as I can, 30 min drive. I'm driving up the interstate, headlights off, using my LED Lenser flashlight.

I nearly make it home and praise God, stall at a good place, I had called my wife to come and find me if I'm not home by a certain time. No cell service where I stall at.

Someone I know pulls up to help and as we have the jumpers on we notice as we pull around on the positive harness coming from the battery the lights with the door open go from dim to bright. So the problem is in the wiring. Problem is it is a jumbled mess of wires. Not sure how to figure out where the problem is, thinking the alt to pos. wires. I stalled out and told him my wife was coming. She came and I just let the battery charge with jumpers enough to make it home. This sucks. Electrical problems suck.

I noticed where the positive side comes into the PDC, underneath the front cover there is a hard section, almost plastic, perhaps that is the fusible link, because as I was waiting I cut open the tape and plastic wire protectors and found nothing from the alt to battery. There is still some sections I haven't opened up though.

So I don't think this has anything to do with a ground. My alternator, tested good three times, and at 213,00 miles it is the original.

CCKen

^^^^


The fusible Link is a 10 Gauge Green wire spliced to the Black/White tracer wire that goes to the alternator B+ connection.


View the pic of the end of the PDC below. You can see the Green wire.


Remove the Green wire connection at the PDC bus bar and remove the B+ wire at the alternator.


Using a digital Ohmmeter, set to the 200 Ohm scale, read between the alternator end of the wire and the fusible link end of the wire. You should read continuity. Wiggle the wire and see if the resistance changes.


Any resistance above 1 Ohm may indicate a bad fusible link or a bad splice between the Green fusible link and the B+ Black/White tracer wire.


If the fusible link is suspect, unwrap the wire harness to get at the fusible link and its splice and feel along its length. Any irregularity is cause for rejection or the fusible link. Any discoloration of the fusible link is cause for rejection.

Jon Iwanyszyn

Thank you for the reply but I got a reading of 0.2 ohms, same as holding the probes together. It stayed that way no matter how much I wiggled the green wire around.

Last night I charged my battery off my Tahoe, since I only work a short distance from home. When I started it up this morning, my voltage gauge was reading 14. However when I got in to leave work it was showing 12 v, back to running on battery.

I think these bumpy gravel roads are moving a bad connection around, what about the green wires from the alternator? Any other thoughts, like I said, after having a jump, I could see the lights dim and go bright when the guy was moving the mass of wires from the + battery terminal.

I just thought of this, since I bought a new battery, could I possibly have gotten a bad one, seems unlikely, given the problems going on.

CCKen

Do you have a Jeep Cherokee Factory Service Manual?


If not, I suggest you download a pdf version of the manual from Pacific Coast Manuals ($7.95).


http://www.pacificcoastmanuals.com/j...e_manuals.html


In Section 8C it describes the charging system, and in Section 8W-20 there is a wiring diagram of the charging system. Section 8W-30-10 has a wiring diagram that shows how the Battery Temperature Sensor is wired in.


Those Green wires are the field control circuit wires from the PCM internal voltage regulator. The Battery Temperature Sensor is used by the PCM to vary the charging rate (based on battery temperature).


The two field control wires pass through a connector (C108) located between the radiator overflow reservoir and the battery. If the connector is compromised with corrosion or is loose it may cause voltage regulation problems. Inspect it.


The Battery Temperature Sensor is a disc located in the bottom of the battery tray. The connector for it is located down low between the right inner fender and the battery. This sensor has been known to screw up alternator output due to a corroded connector. Remove the battery and inspect the temp sensor disc and its wave washer installation, then uncouple the sensor connector and inspect for corrosion.

Jon Iwanyszyn

I will check all that when I have the time.

One part of me thinks this is just an alternator issue, I have heard many complain that the testers at autozone and other places say it is good and it not be. My friend at work told me of a place that will rebuilt it for $30. However I don't want to waste the time or money. I mean 213,000 miles on an original, and now that I search, many people are complaining of an alt. passing the test multiple times at one store and failing at the next.

One more hint, after fully charging my battery with jumpers, the next morning my voltage gauge will read 14v. That would have to mean the alt. is working right?

Jon Iwanyszyn

Well, I decided to go have the alternator rebuilt.

As fate would have it, while I was waiting for it to be fixed, I actually ran into the Advanced Auto guy who tested it at Walmart . We chatted for awhile and he told me that he knew it was bad despite it testing good. He said he doesn't trust the testing machines at all, he has seen alternators which are actually making noises when spun by hand test good. He said he was not allowed to say anything and was dying to.

$30 later, put the alternator back in, good to go. They showed me the old brushes, they were shot, should have known better. It is amazing that the original lasted for 213,000 miles. Thanks for all the help. I learned much, and the take away is, never trust the testing machines.