Will the Car Start with a Bad Alternator? A Comprehensive Guide

Will the Car Start with a Bad Alternator? A Comprehensive Guide

The alternator is a crucial component of a car’s electrical system. But what happens when it goes bad? Can the car still start? This article delves into the intricacies of a car’s alternator and its role in starting a car.

Understanding the Role of an Alternator

The alternator is responsible for supplying current to the vehicle’s electrical system and charging the battery. When the engine is running, the alternator is the main power feed for the car’s electrical system. The battery, on the other hand, is designed to be used as a power source to start the engine.

Signs of a Bad Alternator

A bad alternator can manifest in several ways. These include a battery light in the instrument cluster, interior and exterior lights going dim, slow power windows, and difficulty starting the engine. The failure of an alternator can be categorized into insufficient charging and overcharging.

Starting a Car with a Bad Alternator

Yes, a car can start with a bad alternator, but it’s not recommended. If the battery is fully charged, no damage is caused when driving with a bad alternator, although the car will only run until the car runs out of stored power. However, allowing the jumper cable to be connected longer than necessary can ruin the vehicle’s electronics and cause serious problems.

How Far Can You Drive with a Bad Alternator?

With a faulty alternator and a fully charged battery, you should expect about 30 minutes of operating capacity or about 30 miles. Most cars draw 20-30 Amps while operating and have a battery capacity equivalent to about 50 Amp Hours. But car batteries are not deep cycle batteries, so they will not continue to power the car beyond around 50% capacity.

Jumpstarting a Car with a Bad Alternator

Jumpstarting a car with a bad alternator does not cause damage or present a danger to you. However, it’s a temporary fix. A bad alternator can’t recharge your battery, so you’ll have limited electrical power. Ensure the vehicle providing the jumpstart has a healthy alternator to avoid further complications.

What is the difference between a bad battery and a bad alternator?

Your car’s battery has a crucial role in starting your vehicle by providing the necessary energy.

It also serves as a backup power source for your car’s accessories when the alternator is not functioning at full capacity, which can happen frequently in city driving or traffic jams.

Additionally, it powers any accessories that need to be on while the car is not running, such as a security system or dashcam.

If your battery is not functioning properly, you may experience difficulty starting your car or notice slow cranking when turning over the engine. A clicking sound when attempting to start the car can also indicate a weak battery.

Your car’s alternator is like a little power generator that keeps everything running smoothly.

It not only provides electricity for all the accessories in your vehicle but also recharges your battery at the same time.

The voltage output of an alternator typically falls between 13 and 14.5 volts, while the amperage output can vary depending on the specific vehicle.

For most passenger cars, the maximum amperage ranges from 130 to 200 amps, but there are even higher-rated alternators available, reaching up to 400 amps for certain applications.

If your alternator is acting up, you may notice signs such as a dead battery even after jumpstarting, dashboard warning lights, or electrical failures.


While a car can start with a bad alternator, it’s not recommended due to the potential damage to the vehicle’s electronics.

It’s always best to address the issue as soon as possible to prevent further complications. Remember, regular maintenance and timely repairs are key to the longevity and performance of your vehicle.