Every where I went including nissan dealer told me it was the alternator but I replaced it three times now and still the same problem

These links may offer several ideas:

https://www.askmehelpdesk.com/cars-t...ml#post1973613

https://www.askmehelpdesk.com/cars-t...tml#post241804

Look for a voltage drop across the negative battery termainal and battery post now if the voltage drop is any thing more then .01 then that means its bad. If the V drop is big then remove one fuse at a time and watching the multimeter so see where it goes to 0 and when it does see the fuse cover and that will tell you what circuit is shorted.