What Are Some Common Symptoms of a Bad Alternator?


Quick Answer

One of the most notable symptoms of a bad alternator is a clicking noise that is heard when you attempt to start a vehicle. While this clicking noise may mean that the problem is just the battery, other details are needed to determine if the reason the vehicle is not starting is because the battery is dead, the battery cables are loose or the vehicle has a bad alternator.

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Full Answer

Headlight changes are another symptom of a bad alternator. To differentiate if the problem is the battery or the alternator, complete a headlight test on the vehicle. Start the car, turn on the headlights and press on the accelerator while the vehicle is still in park. Have a spotter check the headlights while the accelerator is depressed. If the alternator is bad, the headlights will dim, flicker or become brighter. If the headlights do not change, then the alternator is probably good.

Another way to check the alternator is to complete a battery test on the vehicle. Start the vehicle, open the hood and remove the negative battery cable. A bad alternator will cause the vehicle to stall out and die. If the alternator is good, the vehicle will continue to run while the negative battery cable is removed.

A parts store can use a terminal to determine if the alternator is bad. If the alternator is good, it should test between 12 and 13.5 volts. A lower number typically means the alternator is bad and needs to be replaced.

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