8 Signs That Your Car’s Alternator Is Failing


The alternator is an important part of your vehicle’s electrics. It works like an old fashioned dynamo, turning motion into charge that’s used to keep the battery topped up and the electrical systems functioning correctly.

With the big demands on power from the modern car, any problem with the alternator can cause systems like engine management, entertainment, climate control and even the dashboard to work intermittently or perform poorly.

If your alternator is suffering from problems then it is advisable to get it looked at ASAP. Problems could accumulate over time and in the worst case scenario you could lose power suddenly when out on the open road or motorway.

What are the symptoms of a faulty alternator?

The following warning signs could give you an early indication that your alternator needs attention:

Warning lights

Our first sign is our most obvious. Many modern cars are fitted with a dashboard light that illuminates when you have a problem with the alternator. Most typically this will be shaped like a battery or could be labelled with ALT or GEN on older models.

As with all lights, never ignore this warning even if the light goes out after a while, as this could be down to an early indication there is trouble with your alternator when you are putting a high electrical demand on the circuits. Get it checked out ASAP.

Dim or Flickering lights

One tell-tale sign of alternator problems is the headlights and dashboard lights beginning to work intermittently or starting to flash. It’s a sure sign that your alternator cannot provide the power that’s needed to the vehicle’s systems. If the problems with the lights happen when you are pressing down on the accelerator, turning on the windows, cranking up the stereo and so on, then you may well have your cause.

Issues with Additional Features

When your alternator is malfunctioning all the systems in your car that require electrical power may start to go haywire. Issues with the power windows, central locking, dashboard lights and even your air con and stereo could start to occur.

You may notice that some systems retain power but do not work at the usual levels, for instance your power windows may be slow to respond and take an age to wind up or down or your power seats may have trouble moving when you push the controls.

Whilst the alternator could be one cause behind these problems, issues with your ECU or car computer could be another culprit. Whatever the reason be sure to get your car checked out as these issues could be serious.

Battery Problems

Your alternator helps keep the car’s battery charged.  Low battery levels can actually be resolved by taking the car out for a good old trip when the alternator is working correctly. However, if the alternator is having problems you’ll notice that the battery drains significantly faster than normal.

One way of diagnosing alternator problems is by charging your vehicle’s battery and then restarting the car. If the battery is the problem then the car will start, the lights will work, but will then become dim over time indicating a charging problem. But if the car gives you trouble starting, then the issue is probably with the alternator.


alternator with drive belt

Many of the parts that help your alternator rotate to produce electrical current can become a little on the noisy side when they are wearing out. For instance the serpentine belt often becomes loose with age and squeals as it tries to find purchase on the alternator wheel, or the internal bearings could wear resulting in a grinding and growling sound.

Put these symptoms together with some of the others on our list, such as poor performance and failed starts and you may be able to finger the alternator as the culprit.


Belts are the key to the alternator’s operation. This system of pulleys helps the alternator turn the rotational power of the car’s movement into electrical power. If a belt isn’t working correctly then it will generally heat up causing a melting smell within the cabin of your vehicle.

If you do notice the smell of burning rubber, which is quite distinct, in your car, then you may have a loose belt slipping on the alternator, preventing it working efficiently. Take a look under the bonnet and see if tightening the belt solves the problem and gets rid of the odours. If nothing changes then you should take your vehicle to a professional mechanic.

Regular Stalling or Trouble Starting Your Car

One of the first signs that you’re having trouble with your alternator is difficulty starting your vehicle and keeping it running on the road. Trouble is there are many other issues that can cause these problems and you need to be able to effectively diagnose the problem.

The alternator powers up the spark plug system, which in turn ignite the petrol or diesel in your pistons. When the alternator stops delivering a full whack of charge there may be insufficient power sent to the spark plugs to keep the engine going, causing it to choke and stall for no reason. Ignore this problem and eventually your car might seize up altogether.

Visual Signs

If you find that your electrical system is giving you all kinds of problems it might not be the alternator. It could well be the one of the belts connected to this part giving up the ghost.

Open up the bonnet of your car and have a quick look around. You should be able to see if the belt is sagging, which means it’s too loose, or extremely taught, which means it’s too tight. Cracks and wear in the belt should also be another warning sign that you’ll be able to spot during your inspection.

And Finally

Need to replace your alternator? You can get all the tips you need from our handy helpful guide that shows you the information you need to perform this replacement yourself. Otherwise make sure you check with your friends and family to find a good garage where you can get the work done for a reasonable price.

This entry was posted in Maintenance on by Justin Smith.

About Justin Smith

As the man at the helm of BreakerLink, it is no surprise that its Director, Justin Smith, has always had a keen interest in cars, bikes and most things wheeled. Having spent over two decades in the car parts industry, Justin combines his passion that since 2002, has successfully united those looking for new and used car parts with the breaker that supplies them. Follow Justin on LinkedIn.

Disclaimer: These articles are for guidance purposes only. If you have any questions regarding any matter relating to your vehicle we would recommend that you seek the advice of an appropriate professional. We accept no responsibility or liability should you suffer financial or personal damages in relation to the advice stated on this website.