i have a 99 f150...the alt went out.i took it to advanced and tested it and said it was bad..i bought one and it isn't workin...took it back and got another and it does not work,could something be shorting out the alt?surely i havn't gotten 2 bad alts...

 

its possible, i had to change out my dads alternator on his chevy 3 different times from 2 different stores as the ones from autozone are usually remanufactured.

 

If they are "rebuilt", YES, you can get several bad ones and just trial and error till you get a "good" one.

 

spend the extra 50 bucks and buy a brand new one