Hello,

I have a 1984 F-700 truck with a 470 V-8 engine.

It was noted that the battery would drain to dead all of a sudden. I inspected the vehicle and noted that the BAT wire connection on the post on the alternator was loose. I torqued it conservatively and when reconnected battery neg there was a dead short. I disconnected the BAT wire on alt and it went away. I reconnected and it re- appeared. Removed alternator and I heard a loose debris in the alternator and occasionally it would jam the stator.

I was sure that the alternator was bad and I replaced it with a re-man from NAPA. Same circumstance.... when BAT post on alternator was connected there is a dead short. I opened the new alternator and saw that the isolated by plastic bus bar attached the the windings would slightly touch the case of the alternator. I removed a little metal from the bus to attain an air gap and re-assembled/reinstalled. Same circumstance when connecting the battery. I unpluged the "electronic regulator" and the problem remains.

I convinced NAPA that the alternator was a defect and they replaced it with a third alternator.. it has the same circumstance.... now I am beginning to doubt my x-shoot skills and understanding of how it works.

On the bench, just me, the alternator and a battery.... should I have a dead short circumstance with the battery (+) connected to the BAT post on the alternator AND a solid ground connected from the alternator chassis to the battery (-) NEG ?

This is an motorcraft alternator with the additional FLD and STA disconnected..... or connected....

What is the chance I would see three defective alternators on the same day?

Thank you for your anticipated reply and wisdom...

Kurt

I sure could use some help with this ....