7 Signs of a Bad Alternator

The alternator, a crucial vehicle component, is responsible for charging your car battery and powering electronic accessories like headlights and radio. If your alternator fails, you might find your car refusing to start or running only briefly. Yet, before reaching such a drastic stage, your vehicle will likely display one or more of these seven symptoms of a faulty alternator.

1. Lights Too Dim or Too Bright

As an alternator deteriorates, it supplies uneven voltage to your electronic accessories. This inconsistency often results in under- or over-performing devices, like headlights, that are either too dim or excessively bright. Flickering lights or lights that irregularly switch between bright and dim can also be a sign.

2. Battery Drains Quickly

Although a dead battery can sometimes be due to natural end-of-life or accidentally leaving headlights on overnight, it can also signal a malfunctioning alternator. A faulty alternator might not sufficiently charge the battery while the engine runs, draining the charge faster than usual. To confirm if it’s a battery or alternator issue, jumpstart your car. If it stays running, your battery might need replacement soon. However, if it dies shortly after jumpstarting, it’s likely your alternator isn’t adequately powering the battery.

3. Slow or Failing Accessories

An underperforming alternator can result in slow or non-functional accessories. For instance, if your windows are slower to roll up or down, your seat warmers feel different, or your speedometer and other instruments start behaving erratically, these could all hint at an alternator issue. Modern vehicles often have a priority list programmed into the car instructs the onboard computer to cut power to nonessential accessories when the alternator is underpowered.

4. Difficulty Starting or Frequent Stalling

Struggling to start your engine could suggest that your alternator isn’t charging the battery sufficiently. Turning the ignition key might only result in a clicking noise instead of your engine’s usual sound. Moreover, frequent stalling while driving could indicate that the spark plugs aren’t receiving enough power from the alternator to keep the engine running.

5. Unusual Noises

Unfamiliar growling or whining noises under the hood could signify alternator issues. Such sounds can occur when the belt turning the alternator’s pulley misaligns or rubs against the side of the pulley or when the bearings spinning the rotor shaft are deteriorating.

6. Burning Rubber or Wire Smells

A distinct burning rubber or wire smell might mean that certain parts of your alternator are wearing out. The alternator’s drive belt, subject to constant tension and friction, can wear out and produce a strong burning rubber smell. Also, an overworked alternator or one with frayed or damaged wires can lead to a burning smell similar to an electrical fire.

7. Battery Warning Light Illuminated

A lit battery warning light on the dashboard is often mistakenly associated with a battery problem alone. However, this warning light signifies a potential issue within the car’s broader electrical system, including the alternator. Alternators operate within a specific voltage range, typically between 13-14.5 volts. If your alternator’s voltage drops below or exceeds this limit, the battery warning light might be triggered.


Knowing these signs can help you identify a bad alternator before it fails and leaves you stranded. Regarding alternator issues, the key is to be proactive—monitor your car’s behavior, listen to its sounds, and seek professional help when you notice any trouble. After all, maintaining the health of your alternator is crucial for your car’s performance and peace of mind.