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What Your Car's Battery Warning Light Means

Every vehicle has a charging system warning light — it’s the dashboard warning light that (usually) has a battery symbol on it, or it might say “BATT,” “ALT” or “CHG.” You should see it every time you start your car; it’ll pop on for a few seconds and then go out.

battery light alt light yellow batt light red chg light yellow

But if your battery light stays on, or if it comes on while you drive, you’ve got a situation. Let’s look at why the light can come on, or you can jump ahead to read about how long you can drive this way.

Why your battery light comes on

Your car’s battery supplies it with power to start up and operates accessories such as the radio and power windows. To keep the battery in peak condition, your vehicle also has a charging system.

This system consists of an alternator connected to the engine by a drive belt, plus some additional electronic components and wiring. The system makes sure your battery keeps its charge despite the demands on it.

If the charging system malfunctions, your car could stall out and leave you stranded. But before that happens you should see the charging light on your dashboard, telling you something is wrong. 

There are many reasons why your charging light can come on. Some are more obvious than others. If you’re not sure what’s causing the problem, your mechanic can identify the exact reason.

You have a bad battery connection

Even if your battery is in good shape, anything that prevents the full flow of electricity can cause the charging light to come on. This could be loose battery clamps, worn battery cables or excessive corrosion on the battery terminals.

Solution: Look at the battery cables to see if they appear to be in good condition, and make sure they’re securely attached at both ends. Replace any cracked or worn cables. Any corrosion should be cleaned off with water and a wire brush. Wear eye protection, and do not inhale the corrosion dust, or get it on your skin or clothes.

Your alternator belt is loose or worn out

The alternator is turned by an engine-driven belt as you drive, which allows it to generate the power that keeps your battery fully charged. If the belt gets loose, worn or it breaks, it’ll stop working right. You may hear a squealing noise from under the hood as you drive if the belt is loose or worn.

Solution: Tighten or replace the belt.

» LEARN MORE: Get an estimate for your car repair

You have a bad alternator

If the belt is OK, the alternator could just be bad. As your vehicle uses more battery power than the alternator can replace, the battery will lose its charge.

Solution: Your mechanic can replace the bad alternator with a new or rebuilt one. This is a fairly simple repair.

You have blown fuses

Most vehicles have fuses to protect electrical components from overloads and the damage that can result. If one or more of these fuses have blown, your charging system may not operate properly. 

Solution: Check all fuses and replace the blown ones. If the same fuses blow again after you replace them, you have a more serious problem. Get your vehicle to your mechanic right away.

You have a bad electronic component or wiring

Your vehicle’s charging system includes other key components, such as the voltage regulator, as well as the wiring that connects it all together. Damage to or failure of this part of the system can cause the charging light to come on.

Solution: Your mechanic can repair or replace the affected components or wiring.

Get it diagnosed by a professional
 

Can I drive with the charging system light on?

An illuminated charging light means that you have limited time to get your vehicle to your mechanic before it stops running. Because your battery is not being adequately recharged, it will gradually lose power. Depending on the cause and the condition of your battery, you may have around a half-hour, or you may have less.

If this happens to you, reduce the electrical load by shutting off the air conditioning or heat, stereo, heated seats, phone charger and anything else that draws power. Drive right to the repair shop. Above all, don’t turn off your vehicle before you get to the mechanic’s shop — you may not be able to restart it and will need a jump start or a tow.

If this happens at night, you will have less time, because you’ll have to keep your headlights on, which will drain the battery faster. If you see the headlights dimming, you’re almost out of time. 

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