battery light is on on 1995 Ford Taurus

the battery light is staying on . i have had the battery check is good, and the alternator check it is good what can it be?

Asked by for the 1995 Ford Taurus
I have the same model and engine. New battery and alternator about 30,000 miles ago. Light has been on every since. No one can seem to figure out why.
2 more answers
The big question is in the battery test. Was it a simple voltage test or was it a voltage test under load? If it wasn't under load, the test is not going to give a valid reading. A Battery without load can give a 12 volt reading with no problem, however it can easily drop as low as 8 volts or less when a load is applied. 10 volts or less will not excite the alternator, which in turn will not put out the 13.8 votls or more which is necessary to operate the vehicles electronics, electrical devices as well as charge the battery.
Modern batteries have limited life spans...
bad diode in alt. replace the alt. make sure connectors are good and tight on the alt.