Car Batteries

Why Does Battery Light Go On And Off While Driving?

Mike Cross
Updated Oct 29, 2021
battery-light-on-and-off-while-driving

A key component in your car is the battery. If the battery is not charged enough, then the car won’t start. How can you know if your battery is good or not? Well, you can test it, but you can also rely on your battery indicator light working properly.

What does it mean though when your battery light on your dash goes on and off though? Does it mean that the battery is going bad?

Well, read on to find out exactly what it means when the battery light goes on and off while driving and also what you should do about it.

battery-light-on-and-off-while-driving
Why Does Battery Light Go On And Off While Driving?

Battery Light

The battery light serves two main purposes in your car. One is to let you know when there is an issue with the battery, but the other is to let you know if there is something wrong with the alternator.

When the battery light goes on and off while driving, it means you are having some sort of issues with one of these two things.

Normally it is a good idea to check these things out as soon as possible because if either stop working properly, then you will be left stranded.

The battery light on your dashboard is important to look out for a while driving. Sometimes it can be hard to notice it come on as well because it might only blink on for a second or two before going back off. Other times it may stay on longer.

When does it come on?

Depending on when the battery warning light comes on might help you figure out what is wrong. If the light comes on when just driving normal on a smooth road, then it is most likely more of an issue with the alternator not putting out enough charge or not working properly.

On the other hand, if the light comes on when you hit a bump in the road or are going around a curve, then the problem is more likely to be a connection issue with a wire.

This is because a bump or curve can cause a wire that is barely connected to shift and lose connection. The reason your car doesn’t just die when the connection is lost is that your car can run off the battery charge for a while.

Also, if the alternator is working right, then it can put off enough charge to run the car even if the battery is not connected.

Alternator issues

So, now we can get in-depth more on the possible issues that are happening when your battery light goes on and off while driving.

The first and worse one is that the alternator is not working properly. An alternator normal doesn’t just die and stop working.

Instead, it malfunctions and stops working slowly. This means that it will work, stop, and work again and sometimes it will do this quickly, while other times it will be longer between the cycle.

This is why your battery light might come on for a bit when the alternator isn’t working and then go off when it starts working again.

it is important to check your alternator if your battery light starts to blink on and off
It is important to check your alternator if your battery light starts to blink on and off

The alternator is a key part of your car because it helps take mechanical energy from your car and converts it to electrical energy to recharge the battery, so the battery can start your car again the next time it is needed too.

If you don’t have a working alternator, your car will eventually stop working. If it goes all the way out, then your vehicle will die pretty quickly, and you will be stranded.

This is why it is important to check your alternator if your battery light starts to blink on and off. The first thing to check with the alternator is to make sure all the wires are connected properly.

If there are any loose wires, then tighten them. After making sure all the wires are connected, you can test the alternator.

Testing the alternator is easy to do. All you need is a voltmeter. Hook the voltmeter up to the battery and see what the reading is. It should be at least 12 volts.

Then start the car and see what the reading is. The reading should jump up to around 14 volts if the alternator is working right.

If the reading does not move up or if the number starts to drop, then the alternator is not working properly and will need to be repaired or replaced.

You can most likely need to take your car to a shop and have this done unless you are a mechanic and good with cars. If the alternator is fine, but you are still having the battery light come on, then it is time to check the battery itself.

Battery Issues

The first thing you should do when checking the battery is to make sure all the wires are connected tightly. If the wires come loose for moments while driving, then that can be why the battery light is coming on and then going off.

One key thing to do when checking the wires tightness is to also make sure that they are clean. If the connection is dirty, then this can affect it as well. Clean off the battery terminals when checking the wires to make sure there is no corrosion on them.

After checking the wires, you can check the battery. If you haven’t already connected a voltmeter to the battery when checking the alternator, then you can do that now.

You can check the battery by a voltmeter
You can check the battery by a voltmeter

The reading should be at least 12 volts. If it is less than that, then the battery is not holding a charge and will need to be replaced. If it is, then you can go to any local auto tool shop, and most will test your battery for free

They will hook a device up to it, and the device will make sure that the battery is working and charging right. The device can also normally check the alternator as well, so it isn’t a bad idea to have them look at your vehicle even if you have checked the alternator with the voltmeter yourself. This way you will know for sure all your issues are taken care of. For battery maintain, i think you should use this tool to recharge battery.

Conclusion

After checking the alternator and the battery, you should have the problem found of why your battery indicator light keeps coming on and off while driving.

Normally it is a failing alternator, but if it mainly happens when hitting bumps, then it could be as simple as loose wires. Luckily for you, you now know the possible reasons why your battery indicator light keeps going on and off while driving and you also know what to do about it, so if it happens to you, you can get the problem fixed before getting stranded somewhere from a bad battery or alternator.

Mike Cross
Life is too short to drive with stock audio

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2 comments on “Why Does Battery Light Go On And Off While Driving?”

  1. I am having this issue with my 2007 Ford expedition. We have replaced both the battery and the alternator and my battery light still comes on randomly while driving or while idling. What else should we check?

    1. My battery light comes on randomly while driving but iff i use indicators,headlights, brake lights or flash main beam it will go off then come back on later

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