The battery light tells you the system is not charging, if it comes on at idle or low rpm it is likely a weak or failing alternator. The idle being too low can also cause it to come on.
I'm not sure about all of these, but I have a 98 Taurus and the battery light came on. After a few days, the car died altogether and I had to replace my alternator. I would definitely take the battery indicator seriously and have your alternator checked.
what causes the battery light to on a 2005 ford expedition to come on?
Ford Taurus
dome light stays on ford taurus
Remove negative battery terminal for 10 mins.
could be alternator or charging circuit or could be anything got to do with the battery when its draining out loose connection terminal
36R
12v
Check the dome light. These cars are notorous for having a bad door switch.
burn out the fuses
48R-3
Probably a dead battery but you may wish to check your battery terminals for corrosion.