Rick's Free Auto Repair Advice

How long does an alternator last?

How long does an alternator last?

When an alternator fails, many car owners want to know if their failed prematurely and ask “How long does an alternator last?” That’s not an easy question to answer.

An alternator is basically an electrical generator. It has a rotating electromagnet (called a rotor) and a stationary electrical coil (called a stator). The rotor spins on a front and rear bearing and the rotor coils are connected to the alternator’s diodes by carbon brushes that slide on two rotating rings located on the rotor’s shaft. From a mechanical point of view, an alternator contains two types of wear parts; bearings and brushes.

On the electrical side, an alternator contains diodes (one-way electrical valves), the rotor coil and stator coil, and some type of solid-state control module. In older vehicles, the module was called a voltage regulator. In later model vehicles, the voltage regulation feature is included in the car’s ECM. The ECM sends command signals to the alternator to vary it’s output and that requires some type of electronic module in the alternator as well.

Generally speaking, the mechanical parts of an alternator last around 7-10 years or around 150,000 miles.

What makes an alternator fail early?

• Mechanical issues that cause an alternator to fail early
• Excessive drive belt tension causes premature wear of the front and rear bearings
• A failed dampening mechanism in the automatic belt tensioner can cause excessive pulse vibration that prematurely damages the alternator’s bearings.
• A worn drive belt can slip and cause the alternator to work harden to keep up with the vehicle’s electrical needs.
• Improper mounting that causes the alternator to vibrate excessively.

Electrical issues that affect how long an alternator lasts

• A bad battery can cause an alternator to fail early
• High resistance at the battery terminals or alternator connections can cause an alternator to fail early.
• Improper jump starting can damage an alternator.
• Using your alternator to recharge a dead battery can cause it to overheat and fail early.

See this post for more information on testing an alternator.

©, 2021 Rick Muscoplat

Posted on by Rick Muscoplat

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