99 Expedition Charging System Query

[Chris_Davis]

Ok,

Yesterday my 99 Expedition's battery light came on and I noticed the voltage gauge was lower than usual. I drove it for a couple of minutes and the voltage gauge went back to normal (maybe a little higher, as it was probably pushing a larger charge back into the battery) and the battery light went back off.

It's still doing it this morning. Comes on at startup, drive a bit, then goes back to normal.

I called a mechanic and he wants to put it on the machine at $80/hr. He said it could be a circuit grounded somewhere.

Anyone got any ideas?

[fireball0012]

Check the tensoner pully, it may be getting weak.

[Chris_Davis]

Well, I had the mechanic look at it.

No codes were found, so that's ok. His prognosis, is that it's the alternator and that the brushes are most likely not having any tension against the armature. The alternator has 150K miles on it, so I can see where that might be the issue.

When I got to his shop the light had turned off and the gauge was reading fine. The alternator showed it was charging 14.2. But when he got through with his tests, paid and left, the light came back on and the gauge went down. I turned right around and let him check it and the alternator wasn't charging at all. The battery showed 12.6...12.5, etc.

So if I come up with about $381. to replace the alternator, belt (needs changing anyways) and for the 1 hour labor, I can get it fixed.

He stated that if the light started coming on and not going off, to stop driving it. He said the fuel pump would go bad if it didn't have at least 12.6V going to it for operation.

So I need to get it done quick....

He checked the tension on the belt and it was fine.

[jonmark1985]

That sucks that it was so expensive.