Hey guys i have a 08 5.4l bout 160k miles. I noticed last week when i started my truck in drivewsy and was sitting there and i noticed my battery guage was at half point when it always sits at between half and 3/4 so i was looking at it then my battery light comes on. So i gave it some gas and the light went off. So i drove down the street and it was going down still. It gets to 1/4 way and i look down next i notice it shoots back up to where it should be. And was fine all week. Till tonight it did same thing but went almost to 0 and abs light came on. Next thing i know shoots rightback up to normal and stayed there. Abs went off too.l. Anyone have any ideas?

 

I would say your alternator is going bad.It is not hard to test them. Or you could take it into advance auto and they could test it.

 

Would an alternator do that be ok sometimes and going bad others what im saying is do they go bad little by little or all at once

 

Yes.. the voltage regulator in the alternator is taking a crap... a very common problem in our year trucks. Our trucks are very picky about what voltage regulator it needs. I suggest a motorcraft reman to avoid any problems.

 

I think you guys are right it's alternator I got in it this morning and started it, then it was going down again and it went down all the way to zero and then the radio started cutting off lights everything speedometer and then like before it shot back up to normal all the lights came back on and I parked it and tried starting it an hour later and it wouldn't start. Altenator is shot.

 

Classic signs... get a motorcraft reman and be done.