Charging System Warning Light Explained

Is your charging system warning light on in your car? Any vehicle maintenance lights can be worrisome, especially when you don’t know what they are for. It’s important to pay attention to any lights coming up in your dashboard so that your car can continue to run without issue. We’ll take a look at your charging system warning light below so that you can understand what it means and how to address it.

What is the charging system in a car?

Car alternator

The first thing you’ll want to know is what a charging system is. There are many electrical components in your car, like your radio, lights, heater, and similar features and they are all powered by your car battery.

While driving, your car battery will inevitably get drained while providing power to all the electrical components. To prevent the battery from dying out after a couple of minutes, the charging system takes over when the engine starts and produces the power instead.

Your charging system consists of three components: a battery, an alternator, and a voltage regulator. All of these are important for keeping your battery running strong, but the alternator is directly responsible for providing electrical components with the power they desperately need to work while also recharging the battery so it’s ready to start the car the next time your turn the ignition key. 

As a result, your battery maintains its charge while the car is running and never gets totally drained out. Simply put, the battery’s job is to supply power to the starter in order to start the car and the charging system is responsible for producing the current needed to power everything and keeping the battery fully charged.

What is a charging system warning light?

With this in mind, it’s easier to understand what a charging system warning light is. This light will illuminate any time your car’s powertrain control module detects that the current in your car’s electrical system is below a certain threshold, usually around 12.6v.

The icon your car displays when you have an issue with your charging system will vary depending on the vehicle you drive. Some display a battery icon, or there might be a few words that say: BATT, ALT, or CHG. These all relate to your vehicle charging system and mean that there’s something faulty with it. 

You should never ignore any type of charging system warning light because it can cause your car to stall or fail to start in the first place. 

One thing to keep in mind is that your charging system warning light will naturally turn on every time you start your car. This is normal, but if it doesn’t turn off within a few seconds, then there is probably an issue with the system.  

What causes a charging system warning light to come up?

Now it’s all good to know what a charging system warning light means but it’s even better to understand what can cause your charging system warning light to turn on so you can fix it as soon as possible. Because the charging system consists of three main components (the battery, alternator, and voltage regulator), it typically means that something is wrong with anyone of those parts.

Several things can cause this light to illuminate. Here are some of the most common ones:

  • Loose Battery Cable
  • Faulty Wiring
  • Worn or Broken Alternator Accessory Belt
  • Leaking Battery
  • Failing Alternator
  • Blown Fuses
  • Dead Battery
  • Faulty Voltage Regulator

Where to look first

Obviously, the most common cause of a charging system warning light coming on is a faulty or damaged alternator. It could be because of a short to ground condition inside one of the induction coils, an incorrect contact of the brushes or a faulty voltage regulator. In all cases, the alternator will need to be replaced.

The least frequent one is a faulty battery. A bad battery will usually prevent the car from starting in the first place. Since the alternator is supplying power to the electrical system while the engine is running, a dead battery will not cause the engine to stall. In fact, once the engine is started, you could pretty much remove the battery from the engine bay and the engine would keep on working just fine. It’s not to say that a faulty battery may never cause a charging system warning light to illuminate but simply remember that it’s most unlikely.

Keeping this in mind, there isn’t always a perfect answer as to why your light is on. You won’t know what is causing the light to turn on unless you test the alternator first. Replacing the battery will sometimes solve the problem, however, this may be putting a bandaid on the issue. If the alternator is not working properly, it won’t be able to keep the battery fully charged and the problem will happen again soon. If there is any other problem with the charging system on your vehicle, the next battery will encounter issues as well. 

A car battery is only as good as the charging system it’s paired with and can only perform as well as the alternator recharging it.

What happens when a charging system warning light is on?

corroded car battery terminal

You also might wonder what is happening when your charging system warning light is on and what should be your next move.

When the charging system warning light comes up, you know for sure that your car is not getting enough power to run properly. If the light turns on while you’re driving, it means that you only have a small window of time to fix the problem. Should you ignore the light, your car will quickly die. 

If your charging system warning light does turn on, this means you should take immediate action. Turn off all unnecessary electrical features including your air conditioning, stereo, headlights (only if it’s safe), and unplug anything in your cigarette lighter outlet. If you don’t drive straight to a mechanic, your car will most likely not start again if you turn it off before taking it to the shop.

How to fix a charging system warning light problem?

new aftermarket replacement car battery

The only way to make the charging system warning light go away is to actually fix the problem. The first thing to check would be the alternator. Make sure to correctly test the alternator and that it’s producing power according to specs. Then perform a battery and charging system load test to be certain that both components output enough amp to power the electrical system.

If everything seems good, check the engine grounds and electrical connections. Damaged wires and corroded connectors may be the answer. Incorrectly tightened battery terminals can also create an intermittent low conductance condition causing the charging system warning light to come up.

Can you drive your car with the battery light on?

Technically speaking, yes, but not for very long. When your charging system warning light illuminates, you have a very short timeframe in which to address the root cause. If you’re lucky, then you’ll have 30 minutes left of driving time. However, this depends on the condition of your battery and the type of car you’re driving. High-end luxury vehicles equipped with every possible electrical gadget and small car like Honda Civics fitted with super small battery may stall a lot faster than that.

How can you test a charging system?

Auto mechanic testing a car battery using a multimeter

If you notice any issues with your car before the charging system warning light turns on, you can perform a few tests to see if it will soon fail. This includes a visual inspection and using a multimeter. Some problems are easily visible, while others will require a multimeter to see where the lack of power is originating from.

Your visual inspection should include the battery, attached wiring, and your alternator belt. If there is corrosion or acid leaks around your battery, this is an issue. If any wiring is damaged, then this is also a problem. Should the alternator belt be damaged or worn, then a charging system light problem is likely imminent. 

Unfortunately, it’s not always easy to identify the issue by visually inspecting it. This is where a multimeter comes in handy. There are a variety of tests you can perform with a multimeter, including: 

  • A base reading with the car off. (12.4V to 12.6V is good)
  • Base charging system reading with the car on. (13.2V to 14V is good)
  • A reading with all electrical components turned on (load). (0.5V higher than base reading is good)
  • Voltage drop test. (no more than 0.2V drop in either terminal is good)

All of these require you to place the probes of a multimeter on your battery terminal and get a reading under different loads. If your readings are less than the figures listed above, then there is likely a problem within the system.

Closing Thoughts

The most important thing to do when the charging system warning light illuminates is to assess your options. How far is the next auto repair shop? If it’s too far, can you find a safe place to stop to call for a tow truck? In all cases, you should aim to have your car checked by a certified auto technician as soon as possible. This warning light is used to reduce the risk of finding yourself stranded on the side of the road in case of malfunction of a system as vital to your car as the charging system. However, it’s not a perfect solution. To keep the risk of charging system problems as low as possible, make sure to have it inspected regularly and keep your battery fully charged at all times. A correctly maintained vehicle is always the best prevention against car problems.



About Ren R

Ren R
Loves cars and helping others learn how to take care of their own vehicle. Drives a Honda Accord and enjoys every second of it!


  1. Avatar

    My battery is good. When cranked, charging system is at 14.1v……as long as it remains in Park. As soon as I change to reverse, neutral, or drive, it drops to 13.0v. Is this a voltage regulator issue? Mentioned several times, but no specific where or how to solve this potential cause.

    • Jean-Claude Landry


      The first thing I would ask is: are you having any issue with the fact that the voltage drops to 13V? Because that’s a normal operating voltage and I don’t think it should be creating any problem.

      It’s really hard to tell without having any info about the car model or year but I think this might be a normal condition. The voltage drop might only be related to components draining more power when the car is in Drive or Reverse than when it’s on Park… Recent vehicles tend to fall in ‘sleep’ mode when in Park.

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