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Five signs of a faulty alternator

Ellie Dyer-Brown, 4 months ago

4 min read

  • Advice
  • Repair
Alternator video cover image

WhoCanFixMyCar discusses some of the most common symptoms of a faulty alternator

Most people probably know the alternator first and foremost as the component of a car that charges its battery. However, the alternator is responsible for more than just that - it actually keeps your headlights, radio, windscreen wipers and other electronic components functioning when the car is running. 

As such, when your alternator stops working properly there are usually a number of fairly obvious signs. Knowing what to look out for will help you identify and solve the problem before it becomes more serious.

Contents:

Dead battery

Dim or overly bright lights

Frequent stalling

Whining or growling noises

Battery warning light


Dead battery

When your car won’t start, it’s tempting to immediately blame the battery, but the fault might actually lie with the alternator. 

A faulty alternator won’t be able to charge the battery properly while the engine is running, causing the charge in the battery to deplete faster than usual. 

To test which component is to blame, you could try jump starting your car. If the engine stays running, this is a sign that your battery might need replacing in the near future. On the other hand, if it dies fairly quickly, it’s time to have your alternator repaired or replaced.


Dim or overly bright lights

When alternators stop working as they should, the voltage that they provide 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 too bright.


Frequent stalling

If your car regularly stalls or struggles to start, this is a sign that your alternator is faulty. One of the more worrying symptoms can be a clicking sound when you turn the key in the ignition. Likewise, frequent stalling indicates that the spark plugs and coils aren’t getting enough power from the alternator. 


Whining or growling noises

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

These noises happen primarily when the alternator’s pulley becomes misaligned, but they might also occur if the bearings that spin the rotor shaft are showing signs of wear and tear.


Battery warning light

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

When the voltage of the alternator drops below the normal amount - which is usually between 13-14.5 volts - the warning light will be triggered. Since the level of voltage is likely to fluctuate significantly, you might notice the light flashing on and off. 

If the battery warning light appears, you should take your car to a mechanic who will be able to diagnose and fix the problem.


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