2005 Ford Focus ZX3 2.0
My Battery light comes on after 30 sec of running. First, check engine light came on. Found battery had bad cell, changed battery. Checked voltage, Alt putting out 13-18 volts. Changed Alt. New one putting out 13.5 with everything turned on, 13.7 at no load. Have checked grounds, battery post clean.
Scanner has no stored codes, but has a stored statement that voltage high. Have removed ground from battery for several hrs, light still comes on.
Has to be bad wiring coming from somewhere. Try a voltage meter. Are you sure you put the right amp battery or alternator in the car?