Signs of a Bad Alternator

an alternator in a classic car

A bad alternator is one of the most common problems that can occur with a car that is getting on in miles and years. Before you start paying for more expensive ways to fix your car, check to see if your car is exhibiting signs of a bad alternator.

Alternators Power the Electrical System

An alternator is any kind of mechanical device that converts mechanical energy into electrical energy. It does this using alternating current. While alternators are used in many different situations, the word "alternator" is often used to refer exclusively to an alternator inside a car. When inside of your car, an alternator powers the electrical system as well as keeping the battery charged. If your alternator does not work properly, your car's engine will not run because the electrical system will sap all the energy from the battery. If you suspect that your alternator is not working, you should talk to a mechanic right away to replace it.

Bad Alternator Symptoms

Knowing the symptoms of a bad alternator will help you to diagnose the problem to the exclusion of other problems that your car might have. These symptoms include the following:

  • If you notice that your instrument panel is dimming and coming back on, this is a sign that your alternator might be on the fritz. Similarly, if your instrument panel is dimming slowly, your alternator has probably died completely and it's only a matter of time until your battery is drained.
  • Another related symptom of a bad alternator is a car engine running weakly and then powering up again. This will occur when an alternator begins to fail, intermittently not putting out enough power to power the engine properly before returning to the proper level of power.
  • When you have a bad alternator, your battery will drain every time that you run your car for any length of time. This means that you will have to jump start your car just about every time that you have to start your car. If you notice that your car needs a lot of jump starts, the origin of the problem might not be the battery -- it might be the alternator.
  • An alternator making strange noises is a sign that there is a problem with the device. If you alternator is working properly you shouldn't even know that it's there. Listen for a rattling noise in the area of your serpentine belt. This is the sound of a bad alternator. You might have to open the hood of your car to hear this sound.
  • Stalling out completely is a sign that the alternator might be nearing total death.
  • If you have a voltmeter you can check this to see if your alternator might be having problems. If you rev the engine and the voltmeter gauge drops, this is a sign that your alternator is having trouble.

If your car is displaying symptoms of a bad alternator and you want a final word on the matter before you bring your car into the shop, many auto parts stores will hook your car up to a diagnostic machine to see how your alternator is working before your bring it into a mechanic. This is a far less expensive option than having a mechanic diagnose your car's problem.

Fixing Your Alternator

If you suspect a problem with your alternator, you should look into it immediately. In the event that your alternator is dying, you will want to get it fixed before it goes out completely. In a worst-case scenario, you might find yourself far from home with no means to contact a tow truck and a car that won't run or restart.

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Signs of a Bad Alternator