Alternator/electrical nightmare!!!!! Plz help!!!

[greenmachine001]

Ok guys I've got an 86 m1008 with some serious charging issues and I need your alls help badly! Everyone I ask nobody knows! Ok so the truck is not charging and keeps blowing the **** out of the driverside alternator for some unknown reason,the alternator has been rebuilt 4 times now and still dim headlights when turned on and dead alternator. It tests good when first installed on the truck and idling.. until its drove then its gone,reading 10V on the driverside and 25v on the passenger side alternator. I'm thinking maybe something is letting 24v randomly back feed back into that alternator causing it to blow....Voltmeter is not working correctly and There is an old slave cable just laying in the back of the truck thats worn pretty bad if that could be causing the problem? Starter maybe? Plzz help!!

 

[davidkroberts]

go into the resources section here and get the wiring diagram from the CUCV manual. Trace the wires from the altenator back through the wiring harness to the firewall above and to the left of the glowplug relay on the firewall. That wire should be traced all the way back through to the front battery which is your 12v side of the hybrid system. When you had it rebuilt was it rebuilt as a 12v altenator or a 24v. It should be 12V but doesnt need the isolated ground of the passenger side altenator.

This does sound like a wire routing issue somewhere. You are going to have to follow and check the connections through the harness. You need to PM doghead or just wait until some of the more senior members here that know what they are talking about pipe in. You will know them they have about 4500 post under the avatar

 

[davidkroberts]

what are you talking about the slave cable. Can you post a pic?

 

[greenmachine001]

Oh ok thanks a lot. It was suppose to have been rebuilt as a 12v alternator. I've got access to some original cucv manuals so I'll go through and check it out. The slave cable is kinda like a big cable ran from the junction box through a small hole in the bad with a plug-hookup looking end on it that just lays in the bed,I was told it was a power supply for the radio equipment that was used in the com trucks. It is in pretty rough shape,can see a couple bare wires and some green corrosion on the plug. I dont have any pics yet but Ill get some. I hope I can get this thing figured out its driving me crazy! Thanks man

 

[AZDeuce]

The FIRST thing I would do is trace that "slave cable" back to where ever it connects to the power supply, and disconnect it. that way if the bare wires are shorting out that will at least take that out of the equation and give you one less thing to be concerned about.

 

[Barrman]

I agree, that cable shorting out could be your problem.

When you hook up the batteries with the key and lights off, do you get a spark? If so, then something somewhere on the truck is shorting out.

Oh, the alternator should have been rebuilt as a 12V unit. Technically, it should be a 12 volt isolated ground unit. That only really matters on the passenger side though.

Since it is your drivers side alternator failing. That points to something on the truck shorting out as suggested above in several post. Check, check and then check all the wires again.

 

[greenmachine001]

Thanks a lot guys for the help,I disconnected the slave cable from the grid box where it was running to. I just hate to stick a new alternator on there and not be for sure and it blow the new one again..