I just picked up my 2005 F150 Xlt, Hoping to put pics up later. My Battery light comes on when its idling but when I'm driveing its off. The belt seems tight enough and the place I bought it put a new battery in it. Any sugestions on what it could be?

 

Quite possibly be a diode on your alternator is out.

My DD has the same issue, battery light flickers on and off randomly and after I checked everything, found the alt had a dead diode. Course now I know it's only a matter of time before it dies but I figured I'd replace it when it does and it's been running strong for 1.5 years on same alt still....

 

The "battery" light is the alternator fault light. It's probably a bad alternator, but other possibilities are the belt is slipping or you've got a poor wiring connection.

 

The belt looks like its on tight, I'll check the battery connection, Thank you

 

that happened to my friend truck and it was his alternator

 

I'm hoping the place that I bought it from will fix it.

 

alternator light coming off and on is the brushes on the slip rings are worn out and intermittently making contact. If you replace your alternator that will go away. Try a voltmeter on your battery with the truck not running (key off). Record that voltage- probably 12.2 (with your new battery). then start it, and your battery voltage should jump to 13.8 or something like that. yours is probably bouncing around 12.5 when it's running and this is what triggers your low battery light. it will rise with higher RPMs and trigger the battery light to go out.

My truck acted this way a few months ago and I pulled the alternator out, tore it down, and the brushes were worn deep into the slip rings. I put it on the lathe and could not turn it down to the bottom of the grooves before it peeled off the slip rings. I know you can put new slip rings on, and buy a new regulator/brush pack, but at that point i threw it in a box, sent it as a core for a new one. I think the core is $60 refund or so, so you want to give them your old one. and a new one i think was $215 for the part. If you try to tear it down you will find that you have to de-solder the diode boards, so it's more work that rebuilding the average alternator.

And be careful when you order the new one, theres 2 kinds, (maybe more) for my year of truck, I was told that the electrical connector is either a square connector or a half moon connector, depending on the alternator amperage.

the swap out was a breeze.

 

Thank you, I'll see if I can get someone to hook it up to a voltmeter