my battery light flashes while im driving and it messes with my lights on 2000 Mercury Cougar

it only happens when i drive and it messes with my lights and when i have the air on or heat it messes with it also

Asked by for the 2000 Mercury Cougar
on most vehicles, when the "Battery Light" Flashes or comes on, that generally means the Alternator is not producing enough voltage, meaning it may need to be replaced. If you have a digital volt meter, you can check the voltage at the battery while the car is running. It should be producing at least 12.8 volts.