Hey, ID the wiring that you have. You have the fuse link cable to the B+ terminal on the alt. A ground wire to the alt. case. Probably 2 wires going to the 4 pin connector. What pin letter is used? Correct me if I don't have it right.

 

its my dd and i florida the swamp gets kinda deep in places to get the ground bolt loose use two box end wrenchs one on nut needs to be a six point one on end of stud use 12point box and squeeze them together should come loose

 

from here on out Ill just refer to that 'Main' power junction as to the 'Starter Relay Box'.

So..

Alternator has two connections.
1. Very thick gauge red cable, using an eye-hole connects from the Alt "BAT+" up to the Starter Relay Box with another eye-hole connection. The fuseable link is about 6 inches before that box, and that wire tests good on both ends.

2. I have a 3 pin (+1 slot filled with grease) for a total of '4 pin) connector, that 'clips' onto the black connection of the Alternator.

thats it. I do not believe there ever was a ground specifically, I believe the ground wire is coming from one of the wires in that connector?


that connector goes from the Alt 4 pin connection, up between the battery and Starter Relay Box, into a big black, flat (i believe) 6 pin connection.

Im going to work on that ground here ina bit.
But my question still stands, would the ground from the NEG Battery terminal to the engine block keep the Alt from charging the Battery?

Because when i connect the battery terminals, the car has power. Which means the NEG battery wire IS making a connection or the battery wouldnt start and run the vehicle for so long or at all regardless of being replenished by the Alt.

 

Im going to go get a pic of the wiring setup as best I can here in a bit.
Of the Alt, the wiring harness behind the battery, and the 4 pin connector.

 

Yes, since your alternator is grounded through it's housing to the bracket to the engine. Have you pulled the plug out of the alternator and checked the plug to see if the 3 wires have power with the key on? If they don't, I'd start looking at fuses and tracing wires. I still think your problem is more power-related rather than ground-related. Especially since it worked until you went mudding. Sounds like a blown fuse/short to me.

 

Well if I didnt have a ground problem before, i do now.
Twisting that bolt to get off the ground wires spun it enough to break the wires..i dunno if these were weak before, but two of them are fully broken. (Pics below of ground).

Here are the other pictures.

One is the 4pin connector. You can clearly see it has two metal connectors in the middle, one gets charge, the other doesnt.
The wires are Yellow, and black/orange (im guessing its a faded orange).

That wire runs up into that 6-wire harness. Im guessing the Alternator is grounded through one of those wires, which may explain why only one of them shows power when being tested...?

 

According to the book, the only similar wiring setup to that is for a 4-cylinder. Was yours maybe converted to the 4.0? The yellow wire should definitely have power with the key on.. It's a direct feed from the ignition switch.
You can set your multi-meter to continuity and check from the other wire in that plug to the ground post on the battery. If you have continuity, that's how you tell it's a ground. I'm almost positive that both of those wires should have power. Every alternator drawing in the book shows the alt's grounding through the body of the alternator at it's bolt points, or through a single solid black wire.
You can always run a ground wire from the -terminal on the batt directly to one of the alt bolts if you want to eliminate grounding questions from the equation.

 

well you are correct...I just tested the power (yellow) into the connector again. Thats the one that has power.

PLFS. "F" has power, it is the yellow wire. "L" is the black/orange and does not show power. The other two dont seem to have wires or metal, so Im guessing on my setup, are just redundant for other models/options.

My 87 has always had the 4.0L. So not sure why it would be closer to a 4cyl setup...

But here are the pics, so you can see. Look closely at the letters, its on both the side and the orange bottom.

 

Everything I see says that both of those wires should have voltage with the key on. The yellow wire is not fused coming from the ignition switch. The other wire runs from the ignition switch, through the fuse panel, then through your charge indicator (either guage or light), then to the alternator. You have a blown fuse or broken wire somewhere on that circut.
If you run a jumper wire from the batt+ terminal directly to that black/orange wire, I'd bet money that your alternator starts charging...

 

That "fuse block" is actually your starter motor relay, and the screwpost is the primary distribution point. All of those odd wires you see on the post? Save the one to the battery, they're all "fusible link" wires, and they're your fuses for primary power distribution.

Chances are you've managed to somehow cook the one between your alternator and the rest of the vehicle. When a fusible link goes, it usually has blistered insulation - and manipulating the wire will readily show that there is no longer a wire in the jacket - so it's all floppy, like a soft bit of rubber hose.

Your alternator is rated 61A (base models,) 80A (higher-end Laredo/Limited OR tow package,) or 100A (higher-end Laredo/Limited AND tow package.) You can take a few tacks to replace the thing:

1) Replace with like bit of fusible link wire. I'd have to check, but I think it's a segment of 12AWG fusible link wire.
2) Replace with a pair of fuses - like MAXI40 or MAXI50. Even MAXI30 or ATO/ATC30 should work for the 61A alternator. However, I do not like this option - a fuse should be a bottleneck, and that obviates using them in parallel like this.
3) Replace with a single industrial fuse. You have a few options - the MEGA, AGU, or ANL series will all offer ratings in the 60-100A range (I use ANL fuses rated sixty to six hundred Amperes fairly consistently.) You'll have to rewire slightly to make this happen, but the job is not complex. I offer kits.
4) Replace with a high-current circuit breaker. I know they're out there, but I haven't yet found a series that I like to offer, so I can't recommend any at the moment.

 

I purchased the 100A rated one from AZ (actually 105amp).

I just rewired the Ground wires and cleaned up the Neg Battery end that goes to the block.

There are 4 ground wires spliced into 2 eye-hole connectors, then the NEG Battery cable itself. So 3 total on the block (psngr side). After cleaning the block up a bit, and putting it all back together, I have yet to start it up and test it. (doubting its going to hep though).

Pics below, Im heading out. So Ill get to it more tomorrow.

5-90, the wire from the Alt "BAT+" to the "Starter Motor Relay" is good. Ive tested it on both ends, and even poked the multimeter on both sides of the 'fusable link' near the "SMR" connection. So if the fusable link was bad, would it be getting connectivity at both ends still?

That buldging rubber 'fusable link' section is kind of squishy, but its not deformed or blistered at all on the outside that i can tell. I guess the next step would be to cut it open and see. Then as you said, i would just replace it with an inline industrial fuse (like in one of my pics there is a red fuse going to the engine bay light).

thanks for all your help. If i can get this working, I might be able to do a clean up Alternator reinstall/troubleshooting thread. There really is not a lot out there in any single location like other builds

 

Well, I'm in agreement with cdhebert. Both those wires should be powered. The yellow wire connected to the ignition switch is the field wire that excites the alternator to start charging. The other is the control voltage for regulator sensing. You need both to be powered for the regulator to function.

The sense wire is usually wired to battery pos. or some connection with battery pos voltage. I can't tell where from the schematic. It may come from the battery or the starter relay where all the wires join. As was pointed out you may need to check those fuse links that join there.

Not easy, but see if you can trace that black/orange wire to see where it connects. You may need to run a wire from the battery to that connector to get the alternator charging.

This is IMO why the alternator tests good at the auto shop but does not charge in the Jeep.

I have seen alternators with a short ground pigtail that connects to the alternator case and goes to a nearby ground connection on the engine. It is just added insurance that the alternator is grounded.

Here is a schematic I found that shows the wiring.

Alternator

 

As cdhebert states, this wire has the charge indicator either light or gauge. If it is defective, this would also kill the circuit. The charge indicator must work for the circuit to work.

 

If i were to run a wire from the battery to the orange/black wire that is not getting a charge (by light or gauge), then where in that wire would i splice it in? and to which battery terminal? and if i screw anything up, Im hoping Im able to purchace that connector so i can still plug it into the alternator...

i guess then i would need to replace that part of the harness to get it back to normal..or make it a more permenant, secure work-around...

 

A fusible link wire is just like a fuse - if it blows, you won't have continuity. Period. The visual cue (from the blistered Hypalon insulation) and tactical cue (floppy rubber feeling) are just ways to check it without digging out your meter or test light.

However, those grounds you're holding up (the light-gage ones - about 14AWG - run into the 3/8" rings) look a little shonky. Me being me, I'd:

- Clip off the "two-into-one"-sized rings (the yellow 10-12AWG size)
- Terminate each lead individually with a heat-shrinkable 3/8" ring, or use head shrink over the ring butt
- Clean the contact point with the engine block (wire wheel, emery, sand lightly, whatever)
- Reassemble.

Make sure the cut end of the wire is fully sealed - that's how contaminants get in and screw things up. A small dot of RTV black on the very end, then shrink the tubing around it, works wonders.