Every car and truck with a combustion engine has an electrical system that relies on at least one battery and an alternator. The battery powers lights, the dashboard, and other onboard systems. The alternator converts some of the energy produced by your engine into electricity, keeping the battery charged.
Both are essential for your vehicle to function correctly. If either malfunctions, your car might fail to start, stall frequently, or experience other serious issues. But how can you tell if your car issues are the signs of a bad alternator vs. a bad battery? Here’s how to recognize and differentiate the symptoms of a failing battery and alternator.
Five Signs of a Bad Battery
Most experienced drivers have faced this scenario at least once: turning the key in the ignition only to be met with silence from the engine. While a dead battery is often the usual suspect, don’t reach for the jumper cables or a spare battery just yet. First, check for these signs to determine if the issue is battery-related.
1. Dim Lights and Dashboard
The battery provides power to the electric system in your car, including every lightbulb, LED, and electronic device. If the battery is dying, it might be unable to supply enough power to these components.
To diagnose these issues, you’ll need to start the car’s electrical systems without turning the engine, such as by turning the key to the On position or entering the right mode on cars with a push-button start. Refer to your owner’s manual for the correct procedure.
Once the electrical system is on, check your headlights and taillights. If the battery goes bad, your lights may look dimmer than usual or flicker. These symptoms are due to the battery not providing enough or consistent power.
A malfunctioning infotainment system and dashboard lights can also indicate the battery is on its way out. For instance, some of the indicators in your dashboard may be less bright than usual, or the infotainment screen might look dim or run into bugs, such as a glitchy or frozen screen.
In some instances, specific components may not even turn on at all. The less battery power is available, the more likely your car will cut power to non-essential systems, such as heated seats.
2. Engine Won’t Start Normally
The most common reason a car won’t start is a failing battery. When you try to start your engine, pay close attention to how it responds.
- Engine takes a long time or repeated tries to start. Your battery is most likely almost dead. While you may be able to drive for a while, your next start is not guaranteed. Schedule a car battery replacement service as soon as possible.
- Engine won’t turn at all. The battery is totally depleted. You may need to jump-start your car using another vehicle’s healthy battery. Schedule a battery service immediately for a replacement.
3. Old Battery
The older a car battery is, the less electrical charge it can hold. Most car batteries today are sealed lead acid (SLA), which lose approximately 20% of their capacity within four years. You may have heard you should replace your car battery every four to five years. This is because, after this period, batteries degrade more rapidly until they can no longer hold a charge effectively.
Think back to the last time you replaced your vehicle’s battery. If it’s been over four years, or if your car is over four years old and still has the original battery, now is the time to replace it with a new one.
4. Corroded Battery
As batteries age and are exposed to daily wear and tear, their terminals can become corroded, preventing electricity from flowing out of the battery correctly. While battery corrosion can happen anywhere, cars regularly exposed to humid climates and extreme temperatures are more likely to develop rust and corrosion, including on the battery terminals.
Don a pair of safety gloves, open the hood, and locate your battery in the engine bay. Inspect it for signs of corrosion on the terminals or the cables; they should resemble powdery or rock-like bundles, typically whitish, blue, or green. If you notice extensive corrosion, don’t attempt to clean it yourself. Instead, schedule a battery replacement service.
5. Damaged or Leaking Battery
One of the most severe signs of a car battery going bad is finding evidence of damage or leakage. Besides preventing you from starting your engine, a damaged battery is a severe hazard that can expose you to corrosive chemicals, harm the environment, start a fire, or cause an explosion.
When inspecting your battery in the engine bay, look for the following signs:
- Battery’s body is broken, swollen, bulging, or deformed
- A strong, sulfuric odor
- Fluid is leaking from the battery body
If you see any of these signs, your car may be unsafe to drive. Discontinue driving your car and contact local, trusted mechanics to have your vehicle towed.
Four Signs Your Alternator is Failing
Recognizing the signs of a bad alternator vs. a bad battery is essential to give your car the correct repairs. Here are some of the most common signs and how to recognize them:
1. Engine Starts and Stalls Immediately
If your car won’t start after turning the key or pressing the push button, one of the most important signs of a bad alternator vs. a bad battery is how the engine reacts to your attempt. If, instead of failing to turn, your engine does start but then stalls immediately, the issue is most likely a bad alternator instead of a bad battery.
Normally, when you start the car, the battery provides the initial spark that lets the engine turn. When it does, it engages the alternator, recharging the battery and providing power to the car’s engine, ignition system, and electrical network.
If the alternator is going bad, it might not provide enough power to the spark plugs, causing the engine to stall. Contact a mechanic to have your alternator replaced as soon as possible and minimize driving in the meantime. Repeatedly trying to start a car with a bad alternator can prematurely drain the battery, increasing the risk of replacing both!
2. Unexpectedly Dead Battery
At first glance, what may seem like a battery problem can be an alternator problem. If your battery has gone dead for no apparent reason, verify that ALL of the following apply first:
- You have driven your car recently, eliminating the possibility of a battery self-discharging
- Your battery is less than four years old
- Your battery is in good condition and has no signs of damage
If you are in this situation, your alternator may have gone bad. A faulty alternator may fail to recharge the battery while the engine runs, meaning your battery steadily depletes over time. Eventually, it will run out of charge and go dead.
If this occurs, don’t just schedule a battery replacement, as the new battery will quickly deplete and leave you stranded again. Instead, have a technician inspect your alternator to determine if it needs replacement.
3. Malfunctioning Accessories While Driving
A failing alternator may not consistently supply power to the car’s electrical system, causing certain accessories, such as the dashboard, speakers, or infotainment system, to malfunction. Common issues include:
- Music or speech that sounds garbled when the radio is on
- Glitches on the infotainment screen
- Gauges and indicators acting erratically
While these issues may not stop you from driving, they can range from mildly annoying to potentially unsafe. Consider getting your car’s alternator inspected to determine if repairs or a replacement are necessary.
4. Burning Smell From The Engine Bay
The alternator and the engine are connected by a belt. As the engine rotates, the belt helps convert the mechanical energy into electricity, allowing the alternator to generate power. The same belt also drives many other critical components, such as the power steering pump, the air conditioning compressor, and the water pump.
Over time, the alternator belt can wear out, develop cracks, fray, or become misaligned. As the belt deteriorates, it may lose tension and fail to grip the pulleys properly, often resulting in an unpleasant burning smell reminiscent of burning rubber or plastic.
If you detect this odor, it indicates that your alternator belt is rapidly wearing out and at risk of breaking. Schedule an alternator service and replace the belt as soon as possible. A failing alternator belt can damage several components in your engine bay.
Get Professional Battery and Alternator Service at Hometown
Whether your car is showing signs of a bad alternator or a failing battery, the best solution is to entrust it to professionals. The friendly and skilled mechanics at Hometown Chrysler Dodge Jeep Ram can diagnose any electrical problem in your car, SUV, or truck.
Even if you don’t drive one of our brands, our team is qualified to work on any make and model car. Contact us today to schedule an alternator service.
