Camarozen 3/1/2012Most likely you have an issue with the alternator, however it might also be a wiring issue. Check all of your battery connections for corrosion and loose connections, as well as the wiring to the alternator and engine ground. You can often have the alternator tested for free at a local part store, however it is usual for many vehicles to produce a lower alternator output voltage at idle.
MB 3/1/2012maybe however a bad battery can kill an alternator. Take your vehicle to an autostore and they will provide a diagnostic of the charging system. The battery could have gone bad also even if it is fairly new