
Signs of a Bad Alternator Vs. Bad Battery
It’s frustrating to start your day by finding out your car won’t start. It’s when you realize you will never make it on time and have to figure out how to fix the problem to cut the losses. A red warning light almost always means there is a problem with your car battery or alternator. But to fix the problem, you need to figure out which power source is the culprit: the dead battery or the alternator. As a general rule, if the car quickly turns off after starting, the problem is the alternator. But if it starts and remains on but then fails to start again, then it’s a battery problem.
It’s not always easy to tell. In this article, we will go over the signs of a bad battery or alternator, helping you figure out which is the root of your problem to fix it and get back on the road.
What Is the Purpose of a Car Battery?
Your car battery is an essential component of your vehicle. Its main function is to provide energy for your engine to start the car. It also stores power for your car and delivers electricity to your ignition system. It also helps regulate voltage.
Read More: How to Boost a Car Battery in 7 Steps
What Are the Symptoms of a Bad Battery? 5 Signs to Watch For
If the engine won’t turn, your first conclusion is a dead car battery. However, it’s better not to act on that speculation and make sure the battery is the problem first. Below are 5 signs that you need to recharge or replace your car battery.
1. Dim Dashboard Lights
The main job of your vehicle’s battery is to provide power to your car’s electrical system, including the lightbulb, LED, and electronic devices. If the battery is dying, these components won’t get enough power from the battery.
Try starting the car without turning the engine on to diagnose the issue by turning the key to the On position or entering the right mode on cars with a push-button start. If you’re unsure how to do this, refer to the vehicle’s owner’s manual.
Check your headlights and taillights once the electrical system is on. Dim lights or flickering lights are a sign of a bad battery. It means the battery isn’t providing enough or consistent power.
Another indicator of a dying battery is malfunctioning accessories, like a glitchy infotainment system or dim dashboard lights. Generally, when there is less battery power, your car will cut power to some components and non-essential systems, like heated seats.
Read More: How to Keep Car Battery Warm in Winter
2. The Engine Doesn’t Start Normally
A failing battery is a common reason for your car not to start. The way your car responds when you try to start the engine can tell you a lot. If the engine takes a long time to start or if it doesn’t start the first time around, the battery is most likely dead. It might work for now, but it will fail to start soon. We recommend scheduling a battery replacement service as soon as possible in this case.
If the engine won’t turn at all, that’s another story. It means the battery is depleted and needs a jump start. Find another car with a healthy battery or schedule a battery boost service.
Canada Direct Roadside Assistance provides a battery boost service as part of our roadside assistance services all over Canada and the US. Learn more when you click the links below.
3. Battery Corrosion
Sometimes, the signs of a bad battery are clear. If your battery has corrosion, it could be the issue preventing it from jump-starting. Use a rag or wire brush to remove the corrosion from the battery terminals, then try to jumpstart the car to determine if corrosion is the issue. If the car jumpstarts but can’t be turned back on without jumper cables, then the battery is the problem, not the alternator.
We recommend not cleaning the battery yourself if the corrosion is extensive. In that case, it’s safer to hire a battery replacement service or visit a mechanic shop.
Read More: Car Won’t Start in Cold: Here’s What to Do
4. Your Car Battery Is Old
Your car battery doesn’t last forever. Most car batteries have a life expectancy of 3-5 years. After 4 years, the battery starts to lose some of its capacity until it can no longer hold a charge. Then, it will start deteriorating rapidly. While you can take some steps to lengthen the life of your battery, a dead battery is inevitable at some point. If you’ve had the same car battery for over 4 years, and it starts acting out, it may be time to replace it.
5. Evidence of Damage or Leakage
An obvious sign of a bad car battery is finding evidence that the battery is damaged or leaking. It’s also a severe hazard, as it doesn’t just prevent you from starting your car; it can also expose you to corrosive chemicals. Moreover, it’s harmful to the environment and can start a fire or cause an explosion.
Signs to look out for when inspecting your battery in the engine bay:
- A broken, swollen, bulging, or deformed battery body
- A strong, sulfuric smell
- Fluid leakage from the battery body
Stop driving your car if you spot any of these signs, as it may be unsafe to continue driving. Contact a towing service 1- 866-519-4001 and get your car to a mechanic’s shop as soon as possible.
What is the Purpose of the Alternator?
While the battery starts the engine, the alternator follows by powering the car when the engine is already up and running. It powers the headlights, electric steering, power windows, windshield wipers, heated seats, and radio. While the battery should be replaced every few years, the alternator can last the entire lifetime of your car. However, it can be damaged by wear and tear, prompting you to repair or replace it.
What Are the Signs of a Bad Alternator?
Knowing if it’s the alternator failing or the battery dying can help you fix the problem quicker. Here are some symptoms of car alternator problems.
1. How the Engine Starts
The way the engine reacts to your attempt to start the car is one of the most important symptoms of a bad alternator. If instead of failing to turn, the engine starts but then stalls, it’s most likely that the issue is a faulty alternator, not a bad battery.
That’s because when you start the car, the battery gives off the initial spark before letting the engine turn. After that, it engages the alternator to recharge the battery and provide power to the engine, ignition system, and electrical system.
If the alternator is failing, it won’t provide enough power to the spark plugs, which causes the engine to stall. In that case, you need to contact a mechanic to replace your failing alternator as soon as possible. In the meantime, it’s best to minimize driving, as repeatedly trying to start a car with a bad alternator can drain the battery. Then, you will have to replace both the alternator and the battery.
2. A Dead Battery Out of the Blue
If your battery dies unexpectedly, you may think there’s something wrong with it. However, if it happens without a clear reason, the alternator might be the real issue.
A process of elimination can help you determine if it’s the alternator or the battery. If you’ve driven your car recently, it means that the problem isn’t the battery self-discharging. If the battery is in good condition, has no sign of damage, and is less than four years old, then it’s not the main problem.
The alternator recharges the battery, meaning a bad alternator may fail to do so, causing the battery to deplete quickly and steadily over time until it runs out of charge and dies.
While scheduling a battery replacement might seem like the right move, it won’t help much. The new battery will quickly deplete and leave you with the same problem. Instead, visit a mechanic and have them inspect your alternator.
3. Malfunctioning Car Accessories
A bad alternator may fail to consistently provide power to the car’s electrical system, which causes some car accessories, like the dashboard, speakers, or infotainment system, to malfunction. For example, if the radio sounds garbled when it’s turned on, the infotainment screen glitches, or the gauges and indicators act erratically, that means that the alternator may be the problem.
You may also see the battery warning light flickering on and off on the dashboard as the alternator struggles to stay in its intended voltage capacity. Your headlights or interior lights may also start running dimmer or brighter than their usual brightness level, depending on your speed.
Another sign of a bad alternator when running electrical accessories, like the radio or exterior lights, is hearing a whine or growling noise from the engine. A whine or growl may also indicate a worn-out serpentine belt or another bad component, like the AC compressor or the power steering pump.
These alternator issues won’t stop you from driving, but they can be annoying and unsafe at times. For comfort and protection, consider getting the alternator inspected by a professional mechanic.
4. Burning Rubber Smell
The alternator belt connects the alternator and the engine. It helps convert mechanical energy into electricity as the engine rotates, allowing the alternator to generate power. This belt is the main driving power behind other critical components, like the power steering pump, the AC compressor, and the water pump.
If the belt loses tension and fails to grip the pulleys properly due to deterioration, it often results in an unpleasant rubber-like or plastic-like smell. Upon detecting this odour, it’s best to schedule an alternator service and replace the belt as soon as possible before the belt breaks. A damaged belt could damage several components in your engine bay.
Frequently Asked Questions
Can you jumpstart a car with a bad alternator?
Yes, you can jumpstart a car with a bad alternator as long as the battery has enough charge to run the car. A car with a broken alternator will only run for a short time, so it’s important to fix or replace the alternator.
How can I test if my alternator is bad?
There are a few ways to test if your alternator is bad. The first sign of a bad alternator is if it stalls when you remove the negative cable from the battery while the engine is running. Another method is to use a multimeter to check the alternator’s voltage to see if it’s good for use.
How do I test if my battery is bad?
To test if your battery is bad, set the multimeter to 15-20 volts. Then, hook the multimeter to the battery terminals to read the voltage. To learn where your battery voltage should be, check your vehicle owner’s manual.
Why won’t my car battery hold a charge?
To test if your car battery is bad, check its condition for any signs of damage, the voltage, and the state of the charge before charging the battery.
Will your car still crank if the alternator is bad?
The car may start if the alternator is bad, but it will only run on the battery’s charge.
Will a bad alternator drain the battery when the car is off?
Yes, a bad alternator can’t recharge the battery, so it will deplete it entirely in a short time.
Will a new battery work if the alternator is bad?
A new battery won’t resolve the underlying issue of having a bad alternator. The alternator will still deplete it, so you should still fix or replace the alternator.
Why does an alternator go bad?
An alternator may go bad because it has suffered from wear and tear from being on the move. It can get dirty or go bad from driving in extreme temperatures.
Can you drive a car with a bad alternator?
You can drive a car with a bad alternator, but it’s not recommended. A bad alternator can completely damage your battery, so you would need to replace it. Also, if the alternator dies completely, you might get stranded on the road.
Can you drive a car with a bad battery?
You can drive a car with a bad battery, but it’s not recommended. After jump-starting the car, you may stall in stop-and-go traffic. Moreover, the alternator runs the car’s electrical system, but at low RPMS, the battery takes over when the alternator has low energy.
How much does it cost to fix a broken alternator?
On average, it costs between $350-$400 to fix a broken alternator for most car models. If the serpentine belt is also included, the cost increases by $20-$50.
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