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Smaller alt pulley?

I'm trying to find a smaller alternator pulley for my 1999 F250 SD V10. I've
previously added a 250 Amp Alternator to handle the starting battery and the 2
AGM batteries I had cabled to the start bat. Turns out now the alternator is
only charging 12.5 at idle but as soon as I bring it up off idle it starts putting
out 14.5amps.

My alternator pulley is presently 59mm 8groove. Anyone have any ideas where
I might be able to get a 55mm or 56mm 8 grove pulley?

Thanks
Bill
 

fatherdoug

Tonto Papadapolous
I was always under the impression that the alternator didn't start doing it's job until the rpms were higher than idle speed, at which point the voltage would increase from 12.5v to 14.5v.
 
changing the pulley from 58-56mm isn't going to get anything extra for you. My recommendation is to clean the negative ground attachment at the passenger battery where it goes to the block. Drivers side, clean the negative ground at the frame coming off the battery and run a cable from the negative ground drivers side frame to the block. Then add a cable from the alternators positive terminal to passenger battery positive post.

That should get you to 13+v.
Current flows from negative to positive, you need a good ground to start from and a cable to handle the increased flow. Go to Napa and have them make the cables using 2/0 cable and a tin connection lug. Add the ones I mentioned and your truck will thank you.
 

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