I just typed a book and accidently went back a page and lost everything i had wrote... so i will start over

On my 03 F250 5.4L, i noticed on the way home from school yesterday my battery light was on so i checked my scangauge2, reported 11.6-11.7 volts. Got home, took my alternator out and brought it to napa where it failed their test. Bought a new $240 alternator from napa, put it in the truck and started it up and good to go. no battery light, 14.4 volts. drove 20 minutes to dinner and it was fine, drove 2 minutes and it was fine, then when i got in my truck to go home the battery light came on and i was down at 13.9-14volts. This morning headed to school, i was back at 14.3-14.4 volts and no light but just as i was pulling into the parking lot my battery light came on and dropped to 13.9-14 volts.

At this point im confused as to why the light keeps coming on and off and why the voltage only drops a little. Could it be from the napa alternator? Should i get it tested? ive been told these engines are picky and only like motorcraft alternators or weird things can happen like i am seeing. When i get home today im going to get a multimeter on the alternator and see what its putting out, and also check all the battery and alternator and ground connections. Does it sound like im on the right track here? Again, just confused as to why it turns on and off. Ill report back in a few hours to see if the light comes on when i go home from school. Thanks for any replies in advance

 

Is the light coming on at idle or when the engine is at speed?

 

It comes on all the time. my dad thinks i should just bring it to the dealer but id rather just buy an motorcraft alternator and replace it myself in 5 minutes instead of wasting my time/money there...

 

Sounds like another bad alternator.

 

I don't think napa will take the old one back in return...will they?

 

NAPA has warranties on parts. Go talk with them and let them know what is going on.

 

Alright good. My dad is stopping at the ford dealer on his way home and picking me up a motorcraft alt and is going to bring the napa one back tomorrow and talk to them because he has an account there for work.

This morning at school i wiggled that connector wire a little and on my 7 mile drive home, volts ranged from 13.9-14.4 and the battery little came on and off 8 times. usually stayed on for about 10 seconds

 

Replaced with Motorcraft alternator... so far so good