About 4-5 months ago My battery light started coming on. But it would go away as soon as I hit the gas then as soon as I let off it came right back on. Then my altenator finally crapped out and we replaced it. The problem went away for about a month or two and now its back. The light comes on as soon as I start it and goes away as soon as I hit the gas then comes right back on when I let off the gas. The battery is in great shape and the altenator is pretty much brand new. So any help with what this could be is greatly appreciated.

 

load test the alternator. With the vehicle in idle, a/c on, headlights on and switched to high, foglights on (this is the quick driveway method), take a voltage measurement at your battery. It should be ~ 14V

 

I tested it today when I got home from practice and I got 15 volts

 

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 suprised it has lasted this long.usually when the light starts coming on the alternator will not last long. suprisingly 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 daignose,and even harder to explain to a customer.

hope this helps...

 

I am having intermittent battery light problems, too. My truck is an '06 4.6 with about 24k on the clock. My symptoms don't match the OP's, but my dash battery warning light is on quite a bit now. I notice it's on more than it's off, but the type of driving doesn't matter, nor does the position of my pedals (gas on, gas off, idle, high revs, etc.).

I first noticed the light last Sunday (a week ago today) after driving through E. Ohio in some of the worst rain I have experienced in a long, long time. It was pouring.

After seeing the light, I immediately set one of my readouts on the Edge Attitude to display the 'Batt Charge' reading, and it never displays a read out under 14.2 or 14.4.

Is the idiot light indicative of 'throwing a code'? Can my Edge read that code?

 

So the answer to my code question is yes. With the key on but engine off, the Edge read a P0622 code. I will be calling the dealer in the morning, as I'm still under warranty and we're headed off on a trip to VA this weekend.

Jeez... first a leaky 3rd brake light repair two weeks ago now this. BTW - The leaking third brake light got my rear seats wet. We all know what happens to F-150 seats when they get wet.

 

I once had to return 2 brand new alternators before I got one that actually worked. You might as well replace it.

 

The dealer just called, my truck is ready. Apparently there was an open circuit in the alternator, so they went ahead and replaced the whole thing (under warranty).

The guy says the regulator/rectifier is inside the alternator, that it is not serviceable, and requires the replacement of the entire alternator assembly if it goes bad.

I feel that's bad design right there. An R/R is a lot cheaper and easier to repair or replace than an entire alternator. Of course, why it went pear-shaped after only 16 months and 25k miles is beyond me, too. But hey, I'm not an expert or anything.

 

The rectifier is servicable if you take the alt to a rebuild shop. The dealer just swaps out the alt because it takes less time and it is easier than component level troubleshooting.

 

Does anyone currently have this battery light problem? I've had my alternator replaced, which didn't work, and then my battery changed out. After both were replaced the problem went away for a month but now it's back. However, the light turns on so sporadically the dealership can't reproduce the problem so they can't diagnose it. No error codes were logged into the computer's memory either...any tips or advice?