1987m m998 no power to batteries.

[Markerss225]

Ok so first post, I have in my care a 87 m998 with the 6.2 non turbo light duty hmmwv with the glorious 60 amp generator. I have download some manuals and searched a few threads. I've run some basic tests and checked the generator, output is perfect. Cleaned all wire connecting points in, on and around the whole vehicle to no avail. The power doesn't make it to the batteries. The manual refers to a test machine. So I'm asking what the possible culprit could be. Most likely a broken wire? Fuseable link in a wire is what my gramps said. No prior issues related to electrical. Any info appreciated.

 

[Dock Rocker]

Have you cleaned the grounds and or installed a grounding harness?


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[Markerss225]

I believe I have. Bone stock as far as I know. Have not seen any excess wires for grounding. But with a voltage tester body is making good a ground. All accessories work fine other than drain battery.

 

[Action]

Check continuity of the big wire running from the gen to the battery box.

 

[Markerss225]

So after some time I found power all the way to the pcb. An eess box. But nothing coming out. So in the mean time I have a a jumper wire from the generator output to the batteries to get me rolling for now. I do have an inline fuse and a digital voltage gauge on the line to monitor it. But its my only wheels here in puerto Rico doing work. Until the boss can order a new box. I've read that the s3? Is a more desirable system. So thanks for the help.

 

[NDT]

Carefully inspect the connector that goes into the box, water gets into it and the wire can burn off or have a bad connection. Meanwhile there should be no problem connecting the alternator output directly to the battery, most mil trucks are wired like that. Thanks for helping out in PR.

 

[papakb]

In the 60 amp alternator system the heavy 8 gauge output wire from the generator goes thru the control box (ESS, S3, KDS, Nartron, LAU,or Prestolite) then to a stud on the starter. From the starter to the battery the connection is made thru a chunk of really heavy gauge welding wire directly to the batteries thru the large feedthru stud on the trans side of the battery box.

Where a lot of people get confused is on the negative side of things. The negative path is from the negative side of the batteries thru the current shunt that's used to measure vehicle current for the STE/ICE system and then thru to the body directly to a ground stud on the body of the starter. The current shunt is that thing that looks like a brass egg slicer mounted to the inner wall of the battery box. Make sure all of those connections are clean and tight.

Question: When you turn the start switch from OFF to RUN, what does your voltmeter do? The power path is alternator - control box - start/run switch - instrument cluster (thru CB2). So one power leg is thru the control box to the starter and the other is thru the control box to the start switch. This might give you some help determining where the problem is.