Alternator Failure: Telltale Signs & Replacement

The alternator is responsible for charging the battery and providing power to the electrical systems in your car. When it fails, there are certain telltale signs that it may need replacement.

How an Alternator Works

An alternator is a device that generates electrical power in a car. It is driven by a belt connected to the engine’s crankshaft and uses rotational energy to convert mechanical energy into electrical energy. The alternator consists of a rotor, a stator, and a voltage regulator. The rotor spins inside the stator, creating a magnetic field that induces an alternating current (AC) in the stator windings. The voltage regulator controls the output voltage by adjusting the strength of the magnetic field in the rotor. The AC output is then converted to direct current (DC) and used to charge the car’s battery and power the electrical system.


Failing Alternator Signs

There are several signs, up to six, that indicate an alternator is failing. It isn’t uncommon that several, if not all, are present.

Warning light

The battery warning light on the dashboard is one of the first signs that the alternator is failing. If this light comes on, it is important to get your car checked as soon as possible.

Dimming lights

If the headlights, dashboard lights, or interior lights are dimming, flickering, or pulsing, it may indicate that the alternator is not providing enough power to the electrical system.

Strange noises

A failing alternator may make a grinding, whining, or buzzing noise, especially when the engine is running.

Battery issues

A weak or dead battery may be a sign of a failing alternator, as the battery may not be getting enough charge.

Electrical system issues

The car’s electrical systems may not function properly, such as the power windows, radio, or air conditioning, as they rely on the alternator for power.

Stalling or difficulty starting

A failing alternator may cause the engine to stall or have difficulty starting, especially if the battery is weak or dead.

If you are experiencing any of these symptoms, it is important to have your car inspected by a professional mechanic as soon as possible to prevent further damage and ensure the safety and reliability of your vehicle.

How to Replace an Alternator

Replacing a failing alternator is a bit more involved than replacing a car battery, but it can still be done with some basic tools and a bit of know-how. You will need a socket wrench, a set of sockets, a pry bar or large screwdriver, a new alternator, and a belt tensioner tool. For your protection, we recommend wearing work gloves and eye protection gear.

Step No. 1 — Disconnect the negative battery cable

Before starting any electrical work on a car, it’s important to disconnect the negative battery cable to prevent electrical shocks and damage to the car’s electrical system.

Step No. 2 — Remove the old alternator

Locate the old alternator and disconnect the wiring harness and any other mounting bolts holding it in place. Remove the old alternator and keep it aside.

Step No. 3 — Install the new alternator

Install the new alternator in the same position where the old one was located. Make sure that the new alternator is properly aligned with the engine and the belt. Tighten the bolts that secure the alternator to the engine block.

Step No. 4 — Reconnect the wiring harness

Reconnect the wiring harness to the new alternator. Make sure that all the connections are secure and tight.

Step No. 5 — Reconnect the negative battery cable

Reconnect the negative battery cable to the battery terminal. Tighten the cable securely.

Step No. 6 — Check the belt tension

Ensure that the belt is properly tensioned. A loose belt can cause the alternator to not work correctly and a tight belt can cause premature wear of the belt and the alternator.

Step No. 7 — Test the new alternator

Start the car and check if the alternator is functioning correctly. Use a multimeter to check the voltage output of the alternator. The voltage output should be within the range specified in the car’s owner’s manual.

Step No. 8 — Final check

Double-check all connections and tighten any loose bolts. Make sure the battery is fully charged and everything is working as intended.

Alternator Considerations

If you are not comfortable performing this task yourself, it is always a good idea to seek the help of a professional mechanic to ensure the job is done correctly and safely.

See AlsoHow to Change a Car Battery

Image by ake1150 via Adobe under standard license.

Matt Keegan
Author: Matthew Keegan
Matt Keegan is a journalist, media professional, and owner of this website. He has an extensive writing background and has covered the automotive sector continuously since 2004. When not driving and evaluating new vehicles, Matt enjoys spending his time outdoors.

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