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Alternator Repairs

The alternator supplies the vehicle with endless electricity. It takes a lot of juice to start an engine and meet all the various electrical needs of a vehicle. While different batteries can have enormous capacities, eventually the headlights, heater, air conditioner, radio, navigation, and infotainment would all drain the battery of power.

The alternator supplies the vehicle with endless electricity. It takes a lot of juice to start an engine and meet all the various electrical needs of a vehicle. While different batteries can have enormous capacities, eventually the headlights, heater, air conditioner, radio, navigation, and infotainment would all drain the battery of power.

An alternator charges the battery while the vehicle is running by turning mechanical energy from a spinning pulley into a current. The rotor, brushes, and other internal parts of an alternator wear out over time, so replacing it is something everyone eventually needs to do. The following symptoms should give you an idea of what’s gone wrong, but if you’re still not sure, you can always bring your vehicle to Advance Auto Parts for a charging and starting system test.

Alternator issues

How to diagnose an alternator that is failing

If you have a “Check Engine“ light, connect a code reader to the diagnostic port. If you find code P0562, you very likely have a failing alternator (note that codes may vary by vehicle make/model/year). Get it checked out at your nearest e-CAR workshop before it fails entirely.

If you suspect a failing alternator but don’t have a warning light, pop the bonnet and check the condition of the fan belt. If it is glazed and slightly burned-looking, that is an indication that it is slipping. The belt is too loose, so it slips on the pulleys instead of traveling along them. The metal-on-rubber friction heats up the belt, quickly wearing it out. Adjust the tensioner to get the belt just right (too tight can also damage an alternator’s bearings), or just replace the FAN belt since it is among the most affordable car parts you can buy, and it’s a quick and easy repair.

If everything looks good under the bonnet, grab your multi-meter. Set the meter to 20V DC and connect the leads to the battery—positive lead to the positive battery terminal and negative lead to the negative terminal. It should read around 12.6 volts.

Start the engine and carefully check the voltage again. This time it should be at least 14.2 volts if the alternator is healthy and charging the battery. If the voltage is good, turn on the headlights, interior lights, radio, heater, and any other electrical load. The meter should still display above 13 volts. If any of the voltages are below spec, it’s a strong case for a new alternator. Check all your cables for corrosion or a loose connection.

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