dual alternators

gambling209 · Aug 31, 2016

no start on my 2008 f250 after driving it a short distance. jumped it got it home. next time tried to start had to jump it. drove to auto parts store and was told batts good but one alternator not putting out but 13.3 volts. battery on driver side getting less charge. which alternator charges that battery? how do you tell what amp alternator setup that you have? after jumping it this time, it started a few times in a row. all this sound reasonable? figured it is the alternator down in the wheel well?

Zmann · Aug 31, 2016

the batteries are charging together they are not isolated

Zmann · Aug 31, 2016

find a better shop to test the system and take the batteries out of the truck or at least
disconnect one at a time to test them individually if your testing in the truck
the Alts are PCM controlled so some don't trust their diagnosis

gambling209 · Aug 31, 2016

thanks for replies. was going to take them out and test before trying to get at alternator.

f350guy · Sep 3, 2016

I have dual alts also from the factory, as I understand they work independently. Can anyone confirm this?

gambling209 · Sep 3, 2016

battery went bad. you can tell which alternator you have by looking at them. the 120a look like regular ford alternators. the 200 is a nipidenso style. sure I spelled that wrong.

f350guy · Sep 6, 2016

gambling209 said:
battery went bad. you can tell which alternator you have by looking at them. the 120a look like regular ford alternators. the 200 is a nipidenso style. sure I spelled that wrong.

So, on dual trucks one is larger than the other?

If so, which is primary and which is secondary?