Auto Service World
News   June 1, 2023   by Steve Montano

Signs of a failing alternator and how to diagnose

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As you know, the alternator plays a big part in the car’s overall performance. That’s why your customers will want to take care of a failing alternator before it leaves them in an unwanted situation. As an automotive service professional, this is one area that can help you stand out with your customers.

Here are signs of a failing alternator and how you should diagnose them.

Lights are dim or overly bright

This seems like a weird either/or scenario but both of these could indicate that there’s an issue with the alternator. What’s happening is that the alternator is not providing the same consistent level of voltage, so it could be underperforming or it could be overperforming. The lights could also flicker. Take a good look at the alternator if that is the case.

Battery is dead

A car battery can die for a variety of reasons. It could be old and at the end of its life or the driver could have accidentally left their headlights on all night. There are other times when the alternator could be the culprit, though.

Check if the alternator is charging the battery correctly while the car is in use. If it’s not, then the battery is going to die faster than normal. Have the car jump started and see if it keeps running. If it does, it’s the battery. If it dies soon afterwards, then that points to the alternator.

Accessories aren’t working properly

A correctly functioning alternator will be able to handle having other accessories run while someone is driving the car. That includes the windows, speedometer and even the seat warmer. If these things stop working right, then that could mean a problem with the alternator.

Check to see if the windows are rolling up and down smoothly, the display is correct and there are no issues with the speedometer. If there are any glitches, it create a dangerous situation, especially on a highway. Take a closer look at the alternator in this case.

The car is not starting or is stalling

There could be a variety of reasons why a car won’t start. One of them could be that the alternator isn’t charging the battery, which means that you’ll hear a clicking sound rather than the engine.

If it’s not the alternator and the battery, it could be the alternator and the spark plugs. The main sign here is having the car stall while out on the road.  In either case, you are going to have to fix the failing alternator situation.

Whining or growling noises

As a technician, you get used to hearing strange sounds coming out of a car.  Over time, you’ll develop an ear that can tell whether the sound is harmless or if it requires immediate attention. If you hear whining or growling noises from the hood, then that means you want to pop it open and look at the alternator.

One of the causes could be due to the belt that turns the pulley that the alternator uses has become misaligned. Also, you might want to make sure that the bearings have not gone bad. In either case, they could be the source of the whining or growling noises.

The smell of burning rubber or wires

Here’s a situation where your sense of smell can play a big part in determining if something is going on with a car’s alternator. It could very well be that the alternator’s drive belt has worn out due to being next to a hot engine all the time. The result will be something smelling like burning rubber.

An overworked alternator can have frayed wires, which will also result in a weird smell. If your customer comes in complaining of this, then you want to inspect the alternator.

There are a lot of different things to look out for when diagnosing a bad alternator. There could even be a battery warning on the car’s dashboard. it might mean something is wrong with the battery or it could be the whole electrical system. All roads almost always point to the alternator.

By checking on this, you can often fix the problem and have a happy customer back on the road again.

Steve Montano is acting president and general manager of operations at Tucson Alternator Exchange. He started as a rebuilder and has worked as a counter salesman and outside salesman.

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