Ford L8000 Not Charging

jgbanshee · Nov 29, 2011

I have a 1995 Ford L8000 dump truck with the 8.3L Cummins. The alternator will not charge the batteries. Checked the alternator output and even put a new one on and it is good. Still only 12.10V at the batteries when running. I checked continuity between wires from the alt to the batteries and all are okay.

barnE · Nov 29, 2011

bad batts, bad voltmeter. Need more checking. How about regulator, may be separate on truck. Dave

to_many_irons · Nov 29, 2011

the alt should have a built in reg . most likly its a delco ?
the battries could be almost dead .but put a charger on them for a bit to top them up .
and its not uncommen to find a alt out of the box bad . seen them cheapo bad for that .
try a load at the alt . there might be a rotten connetcion up in the harness where you cant see .

Jon Hagen · Nov 29, 2011

If the alt is the typical 1 wire, large frame Delco truck alt, it may just need a field flash to restore the rersidual magnetism to get it going.

Pry the rubber plug out of the regulator plug hole on the alt and jumper the #1 regilator terminal to the bat stud for a moment with the engine idling.

1 field flash should restore the residual magnetism in the rotor, so it will self excite after that.

Anonymous-0 · Nov 29, 2011

If it still has the old "blue back" rear half of alternator is blue, then there is a regulator up behind the air cleaner housing, this along with the pigtail that plugs into the regulator can be bad. I'm thinking the 70's ford pickups used the same regulator. chris

Tim in OR · Nov 29, 2011

The L8000 I used to drive had a ford diesel in it with a prestolite Alt. and separate regulator. When it worked, it did fair. The rest of the time it was "Park on a hill, and hope the air holds (to release the parking brake)" I tried to get the shop to change over to a Delco, or lece-neville but they couldn't think that far ahead. Oh well, That truck is long gone.
Tim in OR

jgbanshee · Nov 30, 2011

It is a large Delco alternator with 3 posts (POS R I). Is R the regulator?

jgbanshee · Nov 30, 2011

I am 99 percent sure that this alternator has an internal regulator.

CLTX · Nov 30, 2011

I know what you are going through. I had problems with alternators on a shrimp boat with a 6-71, in that I wasn't getting enough RPMs to the alternator. Much of my work was at 1000-1200 RPMs and I had to go to a smaller pulley on the alternator. How are you exciting the alternator? Some Delcos took pretty high RPMs to excite them. I finally went to a pressure switch, as I had no ignition switch to deal with. Some of the larger Delcos were insulated and required a separate ground wire to get maximum amps out of them. It's probably something simple, but finding the problem can sometimes be a pain.

Ford L8000 Not Charging

jgbanshee

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barnE

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Jon Hagen

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Tim in OR

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jgbanshee

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