There could be several possible causes. Since your question does not give any info regarding when or under what conditions this occurs, it's not possible to know. If, for example, the light only comes on when the vehicle is idling, it's possible that the problem is caused simply because the IDLE SPEED is set TOO LOW. On the other hand, if it occurs when you are accelerating "hard," it could be that the alternator belt is slipping because it is not properly adjusted. The alternator "idiot light" circuit works by monitoring the voltage in the batery/charging system. When the voltage drops below a preset level, the light comes on to indicate that more current is being taken from the battery than the alternator is putting back in. As engine rpm increases, the output [voltage and current] of the alternator increases and at the preset value, the idiot light goes out. IF the problem is not related to engine rpm, then it is possible that there could be a poor connection [loose or corroded] anywhere in the circuit, or there could be an intermitent fault within the alternator itself. There probably are other possible causes, but these are all that come to mind at this time. Most auto parts supply stores, such as O'Reilly, Auto-Zone, etc, can and will attach test equipment to your charging system, and often can diagnose the cause of such a problem. Most usually do this for free.j3h. you either have a bad battery connection , a bad battery or a bad alternator
Also check the serp belt, if it is old it will be stretched out causing belt slip during acceleration.
What does it mean when the airbag light and battery light on 1999 Ford Escort flashes?
what causes the battery light to on a 2005 ford expedition to come on?
With a hammer.
Your battery is not being charged
The battery isn't being charged
Reset the check engine light on a Ford Fusion by disconnecting the battery. On newer cars, once the battery is reconnected, the light will come back on. If this happens, disconnect the battery, turn on the headlights until they go off, draining all the electrical current from the capacitor. Reconnect the battery and the light will go off.
ford transit wont turn over ignition light and battery light on
alternator is not charging battery, or loose - corroded connection on battery cables
Either check your alternator or your battery life and replace as see fit.
Check battery connections, check alternator out put. Exc.
Your battery isn't being charged or accepting a charge
either alternator or wrong size battery