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The battery light or charging warning light, available on the dashboard of your car, indicates malfunctioning or poor charging of the battery. This light illuminates whenever the charging system does not charge the battery with a voltage above approximately 12.5 volts. As this warning may be triggered by a number of things, it is important to take steps to ensure that you know what the actual issue is before replacing any parts.
- Note: This article describes a general check of most common car battery vehicle charging systems and some vehicles may be tested differently.
The troubleshooting process can be fairly straightforward, but there are certain issues that only a professional should address. If the problem appears to be complex, or if the process of troubleshooting becomes daunting, call a mechanic to come and perform an inspection.
Here’s what you can do when your car’s battery light turns on:
Part 1 of 2: React to the battery light
When you first turn on your car with the engine off, the battery light will illuminate and this is normal. If the battery light comes on while the engine is running and the vehicle is being driven, this indicates a problem with the charging system.
Step 1: Turn off everything that draws power. If the battery light is on, then there is still enough battery left to power the vehicle but possibly not for very long.
When this happens, first turn off anything that draws power from the battery, except for the headlights, if you are driving at night. This includes the air conditioning and heating system, the stereo, any interior lights, and any accessories such as heated seats or heated mirrors. Disconnect any phone or accessory chargers as well.
Step 2: Stop the car. If you notice the engine temperature getting warmer or it is is overheating, stop the vehicle on the side of the road to prevent the engine from damage.
If you notice a loss in the power steering, then your car may have a broken a serpentine belt and the power steering or the water pump and alternator may not be turning.
Tip: Try starting your car in a safe location, if the battery light comes on again, do not drive it. Shut off the engine and open the hood to see whether the serpentine belt, alternator or battery have any problems that can be identified visually.
Tip: Always turn off the engine before inspecting the battery or other components.
Part 2 of 2: Inspect the Battery, Alternator, Serpentine Belt and Fuses
Step 1: Locate the battery, the fuse box and the alternator. Locate the battery, the fuse box behind the battery, and the alternator at the front of the engine.
In most vehicles, the battery is located under the hood. If the battery is not under the hood, then it is either located in the trunk or beneath the rear seats.
- Warning: Always use safety glasses or goggles and gloves while working on or near a car’s battery. Follow all safety precautions when handling batteries.
Step 2: Inspect the battery. Look for corrosion on the battery terminals and any damage to the battery.
- Warning: If the battery is damaged or shows signs of leaking, it may need to tested by a professional mechanic and replaced.
Step 2: Remove corrosion from the battery terminals. If there is a lot of corrosion on the terminals, use an old toothbrush to scrub it and remove the corrosion.
You can also dip the brush in water to clean the battery.
- Tip: Mix 1 tablespoon of baking soda with 1 cup of very hot water. Dip an old toothbrush into the mixture and scrub the top of the battery and at the terminals where corrosion has accumulated.
Excessive corrosion at the battery terminals can cause a low voltage condition which makes the starter turn slowly when trying to turn on your vehicle, but it will not illuminate the battery light if the alternator is charging properly once the car is started.
Step 4: Secure the clamps on to the battery terminals. Once the terminals are cleaned, make sure that the clamps connecting the battery cables onto the terminals are secure.
- Tip: If the clamps are loose, use a wrench or a pair of pliers, if available, to tighten the bolt on the side.
Step 5: Inspect the battery cables. Inspect the battery cables that deliver power from the battery to the vehicle.
If these are in poor condition, the vehicle may be receiving insufficient power to start the vehicle properly .
Step 6: Inspect the alternator belt and alternator for problems. The alternator is located on the front of the engine and is driven by a belt.
On some vehicles, this belt is easy to spot. On others, it can be nearly impossible without removing engine covers or accessing them from underneath the vehicle.
- Tip: If the engine is horizontally mounted, the belt will be on either the right or left side of the engine bay.
Inspect the electrical connections on the alternator to make sure they are secure and tight.
Step 7: Check the condition of the serpentine belt. Verify that the serpentine belt is not missing or loose.
Look for any damage or fraying on the belt.If the alternator belt is damaged, it needs to be replaced by a qualified mechanic.
- Tip: If the belt is the culprit, it is likely that there would also be other symptoms like a squealing noise emanating from the engine.
Step 8: Check the fuses.
The fuse box will be located either under the hood or in the car’s interior.
If the fuse box is inside the car, it will be either on the ceiling of the glove compartment or located on the left side of the dashboard near the floor of the driver’s side.
- Tip: Some vehicles have fuse boxes inside the vehicle and under the hood. Check all the fuses in both boxes for any blown fuses.
Step 9: Replace any blown fuses. Some cars will have extra fuses in the fuse box for some of the smaller fuses.
If any of the large fuses are blown, then the system may have a major short and should be checked and replaced by a certified mechanic.
Part 2 of 2: Test the Battery
Step 1: Start the engine. After all of these steps have been taken, the engine needs to be started up again to see if the charging warning light is still on.
If the light goes out after starting the engine, check the charging system for any other problems.
If none of the steps taken do anything to fix the problem, then the problem is probably due to a malfunctioning alternator. This is something that needs to be tested and repaired by a professional. Call in a certified mechanic, like one from YourMechanic, to inspect and repair the battery and alternator systems.
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