Signs of a Bad Alternator

Quite often before your vehicle’s alternator fails completely, it will show warning signs and symptoms that should give you enough time to fix the problem. One of the major signs of a bad alternator is the failing of your vehicle’s electrical components over the span of a few weeks. This will be noticed by electrical components such as your dashboard lights or headlights growing dimmer when you are driving your vehicle. After some driving the lights may become stronger again and it may only be an intermittent problem, but this is your first sure-tell sign of a bad alternator. Eventually, this intermittent problem will leave your vehicle inoperable if it is not looked after, and your vehicle may even die on you while you are driving it. It is important to diagnose this problem as soon as you can to lower the possibility of related repairs, and to ensure that your vehicle does not quit on you when you need it most.

If you begin to suspect that your vehicle may have a failing alternator there are a few tests that you will want to conduct to ensure that you have indeed pinpointed the problem. There are usually four major causes of this particular vehicle issue: the serpentine belt, the battery, wiring, or the alternator. It is important to pinpoint the problem as soon as possible. A faulty alternator will put added stress on your battery which could shorten its life, and vice versa.

To determine if the serpentine belt is causing this issue with your vehicle, you will want to examine the belt with the engine turned off. The belt rotates through a number of different engine components, and the movement of the belt provides power to the alternator by rotating its rotor. If the engine belt is loose, cracked, frayed or the teeth have been damaged, your belt will not rotate the alternator properly and would inhibit the part from generating power.

The second cause may be your vehicle’s battery. You can test whether the problem is actually the battery by performing a voltage test. You will want to leave your vehicle overnight before running this test in order to get accurate results. With your vehicle engine turned off, hook the voltmeter up to the battery. If the voltmeter captures a reading between 12.5 Volts and 12.8 Volts, your battery is functioning well and is not likely the cause of the problem.

Finally, you will want to definitively determine that the alternator is in fact the issue that is rendering your vehicle inoperable. First, check the wiring leading from the alternator, and the wiring leading from the battery. A frayed, corroded or loose connection/wire could very easily be the culprit. If your wiring seems to be fine, then finally we will test the alternator. Turn on your vehicle’s engine and again hook up the voltmeter to the battery. Turn on any component that draws power such as the radio, headlights and internal lights, and then rev the engine up to 2000 RPM. The Voltmeter should be reading around 14 Volts. Any reading that is lower than 13.5 Volts would be a cause for concern that your problem is being caused by the alternator. If you do not have a voltmeter, phone around to local auto part stores. Quite often they will conduct the test for you free of charge (that is if your vehicle can operate enough to get there).

Some people may recommend pulling your battery cables to troubleshoot an alternator problem. This is a terrible idea, as it has been known to kill your vehicle’s engine computer and other electrical components on your vehicle. Do not conduct this test and if your mechanic suggests it, get a new mechanic.

You should be able to pinpoint the culprit when this situation arises by knowing the signs of a bad alternator. This knowledge could end up saving you hundreds of dollars in car repairs.


Hopefully this article has helped you determine the signs of a

failing alternator