Your car is behaving erratically. Headlights are flickering. The battery symbol is flashing. The engine even stalls. These are normal bad alternator symptoms, and if ignored, they can result in a dead car or loss of power at any time.
Luckily, a bad alternator typically gives some warning signs before it dies completely, so you can learn how to identify these signs.
What Does an Alternator Do?
While your car’s engine is running, the alternator generates the electricity that supplies systems like your lights, radio, dashboard, power windows, and air conditioning. It also maintains the charge level of the battery, providing enough power to allow you to turn on your car again.
When your alternator stops functioning properly, your vehicle relies solely on its battery. Once that stored power runs out, the car can shut down.
Common Symptoms of a Bad Alternator
Battery or Charging Warning Light
A battery-shaped light doesn’t necessarily mean that the battery is dead. Typically, it means that it’s experiencing issues with the charging system. Some cars also display phrases such as “Check Charging System” in their message centers.
If this light remains on during operation, have your charging system inspected as soon as possible.
Dim or Flickering Lights
When the alternator is weak, it can cause various headlight-related issues, including dimming, flickering, or sudden changes in brightness. This can happen with the interior, exterior, and dashboard lights of your vehicle.
Electrical Problems
Most modern cars rely heavily on electricity. Issues caused by a failing alternator can lead to numerous electrical problems. Examples include: slow-moving power windows, flickering dashboard screens, radios turning off, and other electronic accessories malfunctioning.
Multiple electrical-related issues can happen simultaneously and point to a more serious problem that needs to be investigated.
Trouble Starting or Engine Stalling
Frequently, a weak battery is identified as the reason behind a problem when starting your car. However, in many cases, the problem actually happens due to the alternator that isn’t maintaining adequate charging levels in the battery, which can lead to multiple jump-starts per day.
Depending on the severity of the issue, the engine can also stall once the battery loses enough power.
Strange Noises or Burning Smells
A worn alternator bearing can create whining, grinding, or growling noises. You can also notice burning rubber or electrical odours, which often indicate electrical problems with either the belt, wiring, or the alternator itself.
Bad Alternator vs. Bad Battery: How to Tell the Difference
Bad batteries and bad alternators frequently show similar symptoms. Here’s how to differentiate them:
- Dead batteries usually show up when trying to start the car.
- Alternator problems often appear when the engine is running.
If you find yourself having to jump-start your car repeatedly because the battery soon loses power, you may have a problem with the charging system, and it should be professionally evaluated.
If testing shows that the battery is the problem, you can look for used batteries instead of automatically buying new.
What Causes an Alternator to Fail?
Alternators wear out over time.
Common causes include:
- Worn bearings
- Damaged internal parts
- Excessive heat
- Fluid contamination
- Electrical faults
- Problems with the drive belt
- High mileage
How to Test a Bad Alternator
Testing a bad alternator involves checking your charging system using the proper equipment. An experienced technician can measure charging voltage and evaluate whether your alternator produces enough power while the engine operates.
You can also inspect the belt, wiring, and battery connections for any visible damage or rust.
Please note: disconnecting your battery while the engine is running can harm electrical components found in modern vehicles.
Can You Drive With a Bad Alternator?
Don’t continue driving with a failing alternator. Once the failed unit stops producing power, your vehicle will run entirely based on what’s left in the battery until it runs out and the engine shuts down. That can leave you stranded or cause the vehicle to stall while driving.
Should You Repair, Replace, or Buy a Used Alternator?
Your best option depends on multiple factors, including the age of the vehicle, repair cost, alternator condition, and whether it can be rebuilt. In some cases, the easiest solution is to replace.
For an older vehicle, buying a used alternator can help keep repair costs down. You can check Kenny U Pull’s inventory of used auto parts to look for replacement options.
How to Find a Compatible Used Alternator
You need the correct alternator for your vehicle, so start with the year, make, model, engine size, and part specifications. Use our inventory tool to see which vehicles are currently available.
If the vehicle you need isn’t in the yard, sign up for vehicle alerts so you know when a matching vehicle arrives.
Is an Alternator Repair Worth It on an Older Car?
An alternator problem doesn’t automatically mean your car reached the end of its useful life. If the engine, transmission, body, and other major systems are still in good shape, replacing the alternator can be a reasonable repair.
The decision becomes harder when the alternator is only one item on a long repair list. If your car needs several expensive fixes and you no longer want to keep spending money on it, you can also sell your car instead.
Frequently Asked Questions About Bad Alternators
Can a bad alternator drain a new battery?
Yes. If the alternator doesn’t recharge the battery properly, the battery keeps losing power and can eventually fail.
Will a car start with a bad alternator?
Yes, if the battery still has enough stored power. The car can start and then lose power once the battery drains.
How long does an alternator last?
There is no exact lifespan for every vehicle. Mileage, heat, driving conditions, and electrical demand all affect how long an alternator lasts.
