2003 Ford focus, 78,000 miles, 2.0 zetec. My battery light comes on at 35 mph. And will go off at 55 mph. It does not have any other symptoms or noises. I chked the battery with a volt meter and it chked ok. No other engine lights have come on. I have changed the drive belt and chked all connections. What could this on off battery light mean?
I would suggest taking it to an autozone or checker when you get the time and have them test the battery and altenator. You might have a bad altenator if it's dropping while driving at the lower speed since it's using power but when you ramp up the speed it makes up for the drain. So just take it in and have them hook it up for free.