bmfshott

Of course the day before I'm suppose to head out on vacation for a bit, my battery light on my 2008 Ford F150 4.6L is coming on. It might pop on and go off in a minute, then I shut the vehicle off and turn it back on and its off.

No issues with starting the vehicle the battery is not dead, and I haven't seen a drop in voltage when it comes on. I'm guessing its something to do with either a connection with the alternator or the alternator itself.

Connection posts are clean and tight. Hooked it up to a multimeter and its at 12 off and 14 when I start it so its charging, alternator plug was on tight... I have no idea, didn't come back on after I checked it out. When the light does come on while drive the dash gauge remains in the middle of L & H... It came on while I had the mulitmeter on and no drop...

I'm out of ideas.

techrep

iTrader: (1)

its either the battery or the alt or like you said the connections in between

lyricspap

i had this issue a few months ago. it started with batt light coming on for a bit then out. i ignored it for a while because truck started fine. then a few weeks later i noticed the volt gauge would spike 3/4 for a while then go back to normal. finally decided to replace alt,figured reg was going, and everything has been fine since.

bonez

It was my alt when my light came on like that.

bmfshott

Found this on another forum and went down and picked up a new alternator. Light hasn't come on since.


"Replace your alternator. I see this problem quite often at work. (I own an alternator rebuild shop) the problem is caused by a worn out slip ring in your alternator. The carbon brushes in the regulator run against the brass slip ring and will actually cut grooves into the ring and will loose contact and cause the unit to stop charging.it is not considered a user serviceable part. I'm surprised it has lasted this long.usually when the light starts coming on the alternator will not last long. surprisingly enough the unit will generally test good,and will work a few days only to do the same thing again. This is a hard problem to diagnose, and even harder to explain to a customer."

DanInTexas

I have been fighting this on my 08 4.6L. My mechanic has put in 5 alternators. The last one is a brand new one instead of a rebuilt one. Light still comes on for about 5 seconds maybe once a day or so.

If you do put in a new alternator. Don't do what my mechanic did. Go motorcraft. The altimas suck