i have a 2000 7.3 f250 with dual bats and alts the bat light came on a few days ago but the truck has been fine until now
now its dead when i jump it it will start but i had a volt meter on the baterie and it was actually loosing volts not gaining them i figure it would be impossible to have 2 alts take a dump at the same time could this be something else before i tear off the alts and have them tested one is easy to get at the other looks like a pita
thanks

 

I think your newer truck has fuses on the alternators. Look in the underhood fuse box, and there should be one or two very large maxi fuses for the output of the alternators, and there will be some regular small fuses for the regulator part of the alternator.

 

thanks i will check tommorow when i get home from work before i tear them off and have them tested
i think its a bad alt though i could get the light to go off some times if i reved it up it would go on and off so it seems like a low output to me and with the higher rpm it may have givin me an extra day or so out of it but even still with two i would imagine they both couldnt be bad unless maybe one was bad and driving on one put to big of a load on the other thus killing that one too
all i know is i wasent planing on spending 350 bucks on alternators tommorow

 

As Franklin2 said you have three small fuses, one (10A #6) is for both A/C Generators "A" circuits plus two 5Amp fuses for each "A" circuits (#5 & #7).

Both A/C Generators "B" circuits run through the two Fuse links, B & H (12 GA each) with the batterys wired in parallel.

So you have a bad fuse #6 Fuse or both Fuse Links bad.

The PCM also turns both A/C Generators off and on.

 

Also, with high dollar alternators, you might be ahead to take them apart and repair them yourself if you are handy, or take them to a auto elec shop and let them go through the alts. It may just need brushes.

 

i pulled the alts and had them tested primary was not working the lower was but when we looked inside it was pretty worn got them both rebuilt for 170 bucks and got to see how to do it for next time