I have a 2001 f150 its not charging enough so we changed belt & alternator...
And nothing it charges 12.3 and goes down to 11 volts sometimes 13.1..
then we changed the fuselink from a newer truck in junkyard even direct wire to batt..
and still nothing same thing so if have any idea just let me know...

 

Ground...

 

Your battery might be the problem if it's not holding a charge. Do you have a lot of aftermarket lights and stereo equipment? You could be running it down faster than it can charged? If not the battery could just be old enough to need replaced.

 

are your wires going to the battery corroded? maybe a bad connection

 

Check for loose connections, the "wiggle" test and then look for loose ground on the block, frame battery, etc. then have the alt. tested with the battery, and have them put a load on it

 

autozone will check it for free

 

thanks for the help it turned out to be some disconnected ground wire when engine was swapped

 

GROUNDS CAN MAKE A GOOD MECHANIC LOOK BAD!!! Small things like that can go untouched or hard to find