Battery light - alternator?

[gregc]

I have a 2000 F250 with factory dual alternators.

In the morning, when starting the truck, the battery light would comes on until a block or two away from the house.

Specifically, the volt meter points to the corner of the battery when I first start it and when the battery light comes on. After the light goes out, the needle points at the left battery terminal.

My suspicion is that one of my alternator's is completely out while the other is on the way out.

How are these setup? I know on a GM there is a sense wire and an activation wire. Are Fords similar? If so, could the problem be with either of those or is it likely the alternators themselves?

Has anyone rebuilt the alternator themself? I've done some Delcos but never a Motorcraft. Is it much different?

[jfines@cox.net]

I would first have the batteries tested. With the exception of the battery light, the gauge sounds normal. As it is getting colder, your glow plugs will be on longer. And with a weak battery, that would cause the light.

As for the altenator, I don't have answers for that, but it should be easy enough to test those along with the batteries.

Also, I would replace everything in pairs. from my experiance, when one battery goes,the other isn't far behind. May be the same for the altenators.

[jfines@cox.net]

Oh, and I always let my truck warm up enough for the voltage to come to normal, before I drive.

[gregc]

I forgot about the glow plugs and the big draw they take. I think tomorrow I'll wait a couple minutes after the wait to start light goes out to see if that is the draw.

Both batteries are fairly new (one not a year old the other not even two years old). I do think there is a drain somewhere though. I tested the amperage this summer while it was just sitting there and it was .3 amps I believe. Doesn't sound like much but I believe it is supposed to be closer to .03 amps. Unfortunately I fried my DVM before I got a chance to track down the draw.

Thanks for pointing out the glow plug draw.

[ProStarPony]

your draw could become an issue but if you can, find a scanner that can self test modules and your GEM, I believe, will set codes for alternators and you can pinpoint which one is at fault if your batteries are OK.