if you have a turbo timer or volt meter it should be running between 13 ish volts and 14 at idle. if its below 12 theres a good chance the alternator is going bad. oh also if the volts dont rise when the motor is at anything higher than idle than the alternator is said cya.. If thats not the case then you have a short somewhere or corrosion on a critical batter cable that is causing a not enough power to be supplied from the battery. oh yes bad grounds as well will do it.