Five Signs of a Faulty Alternator

Most people know the alternator as the component that charges a car's battery. However, it's responsible for more than that - it also keeps your headlights, radio, windscreen wipers and other electronic components functioning when the car is on. 

When your alternator stops working, there are usually several signs. This guide explains what you need to look out for.

Contents

1. Dead battery

2. Dim or overly bright lights

3. Frequent stalling

4. Whining or growling noises

5. Battery warning light

1. Dead battery

It’s tempting to blame the battery when your car doesn't start, but the fault might lie with the alternator. A faulty alternator won’t be able to charge the battery properly while the engine is running, causing its charge to deplete faster than usual.

You could try jump-starting your car to test which component is to blame, removing the cables as soon as possible. If the vehicle dies quickly, it’s time to replace your alternator.

2. Dim or overly bright lights

When the alternator stops working as it should, the voltage it provides to electrical components becomes inconsistent, which usually causes equipment to either under- or over-perform. As a result, your lights might flicker, appear dimmer than usual or even be too bright.

3. Frequent stalling

If your car regularly stalls or struggles to start, it could be a sign that the battery isn't being charged correctly by the alternator or that the spark plugs are receiving insufficient power to get the engine going.

However, stalling can be a symptom of many different car problems, as discussed in this guide.

4. Whining or grinding noises

There are a multitude of noises your car might make, some good and some bad, but if you can hear either grinding or whining, it might be time to have your alternator checked by a mechanic. 

Whining noises often happen when the alternator’s pulley becomes misaligned, while grinding typically occurs when the bearings that spin the rotor shaft are worn.

Check out this guide for more advice about how to diagnose & fix unusual car noises.

5. Battery warning light

When the battery warning light appears on the dash, it doesn’t necessarily mean that the problem is with the battery. It could be a fault with the alternator.

When the alternator's voltage drops below the normal amount - usually between 13-14.5 volts - the warning light is triggered, and since the voltage level will likely fluctuate, it might flash intermittently.

This guide provides more advice about what car warning lights mean.

How much does an alternator repair cost?

According to our data, it costs £523.89 on average for an alternator repair. Below is a breakdown of alternator repair costs for some of the most popular car makes.

Having trouble with your car's alternator? FixMyCar can help you find a reliable local mechanic for a repair.

If you found this guide helpful, you might also like:

• What does an alternator do?

• What to when your car wont start

• What to do when restarting a car that hasn't been used for a long time

• What to do when your car battery is dead

• How much does it cost to replace an alternator?

• Why does my car keep stalling?

• Why are the lights flickering in my car?