Expert: chris ehlerman - 12/16/2007

Question
Friend's car. Ha shuddered and stalled at traffic lights in past week. Lights and switched on accessories will flicker violently prior to stalling. Battery is new but shows slightly low voltage. I disconnected the alternator during idle ( I know the problems associated with this procedure on new cars, but this is a valid method on older cars) and the engine died immediately! Tried this twice and it stalled both times.

Answer
hello tom first the battery needs to fully charged and then load tested. if the battery checks out ok move on to checking the alternator output voltage at idle and then 2500 rpm under load. the voltage output should be between 13.7 to 14.5 volts. you did not mention when the car dies and the lights flicker if the car starts on its own or needs to be jumped. disconnecting the alternator wire on this vehicle will not determine anything and can cause damage to the charging system. also check all battery connections and grounds for good connections as this can also cause your problem. using these methods you should find the problem fairly easy. good luck