Car Shuts Off While Driving and Battery Light Comes On [What To Do]

battery light comes on while driving

Car shutting off while driving is not a commonly occurring problem, but if it is something you are experiencing frequently then it could be an indicator of the condition of the engine.

The engine has several parts with work in harmony to make the car move and keep it moving. The harmony between each part ensures the car can keep going on continuously without breaking down in the middle of the road.

If your car shuts off while driving and the battery light comes on, it could probably be nothing to worry about. But, if it happens frequently then it means it was time you got a thorough inspection of your car.

Car shutting off while driving is usually the result of a bad or weak alternator, problems in the fueling system, or problems in the electrical circuits of the car.

If it happens just once out of the blue, it could be the result of a loose battery terminal and the car being driven over a pothole.

The details are important for this very topic because a symptom such as this is very serious and every driver should be aware of this.

The battery light coming on after the car shuts off is also interesting, read along to find out why.

What Causes Car To Shut Off While Driving?

There are several reasons why the vehicle might “die” while you’re driving. Some causes can be ignored for some time, some can be tolerated for some and some may require immediate attention.

Let’s see what they are;

1. A Weak Alternator

The alternator is responsible to generate electrical power to meet all the electrical needs of the car. When the car is stalling, and the battery light comes on, it means the alternator is weak. It could be a damaged pulley or something wrong with the alternator.

It is usually the magnetic core that has become worn, but a more common problem is wearing carbon brushes or slip rings that have carbon build-up.

The battery does not provide power to all the car’s electrical components. It is generated by the alternator and it charges the battery. Which then distributes to other electrical components.

If the battery light comes on while your car is stalling, it could mean there is a weak alternator and the car idle is not enough to generate the required power.

As the engine revs through the RPMs, higher spark intensity is required to burn the air-fuel mixture. A weak alternator does not generate enough spark intensity to keep the combustion happening.

This causes the car to stall and shut off while driving and the battery light to come on.

Diagnosing

If you have a weak alternator, you will see the battery light come on in the dash. You will also see the brightness of the lamp increasing and decreasing with RPMs.

Repairs

If the alternator is damaged, then you can probably have it repaired rather than having a replacement. Not all mechanics can change just a pulley, and no alternators can change their pulley. But changing the pulley, if it can be, can cost around $150.

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Carbon brushes and slip rings need to be replaced, which costs around. Carbon brushes cost around $100, and slip ring replacements may cost about $200 because they are labor-intensive.

2. Weak Battery

Loose battery and alternator terminals also cause the battery light to come on. Battery terminals come loose due to temperature changes, debris from the road, vibrations, and damage from the road.

Build-up on the terminals is also very common due to the weather, grime from the road, or battery acid. Sometimes the leaking reservoirs of different fluids also create build-up on the terminals.

Diagnosing

You can know for sure if it’s weak charging or a weak battery by idling the car and seeing if the battery light comes on. When the battery light comes on, switch on the A.C. and all the lamps and see if the revs fall.

If the revs fall or the lights start flickering, it is a sign of weak alternator charging. You can connect the voltmeter to take readings to ensure to check the charging level by following these steps;

  • Set a voltmeter to 15 DC volts
  • Clean the alternator terminals
  • Set the black cable of the multimeter to the negative terminal and the red to the positive.
  • Check for the ideal reading of 12.6V
  • After starting the car, the reading should be 14.2-14.7
  • Reading over 14.7 means the alternator is overcharging, and reading below 14.2 means undercharging
  • Turn on all the electronics; lights, fans, radio, and A.C. and see if the readings stay above 13
  • After turning off the car, check if the readings stay above 12.6

https://www.wikihow.com/Check-an-Alternator

Repairs

The battery is usually replaced instead of repaired because replacing is more reliable. A new battery costs around $50-$150.

3. Bad Fueling

As the car speeds up, the engine requires more air and fuel volume to generate more power. A weak fuel pump will not be able to provide the required fuel volume and may cause missing and eventually lead to the car dying. Sediment buildup in the fuel lines or fuel filters may also reduce the fuel flow rate causing the car to stall.

The fuel pump can also fail due to low voltage caused by a weak battery or weak alternator. A bad fuel pump causes the car to shut off while driving and the battery light comes on.

Diagnosing

You can check the fuel pump fuse to check for voltage issues. A blown fuse means an electrical fault in the fueling system. Check engine light will let you know if there is an error with the mechanical parts of the engine. Connect the OBD2 scan tool and the low fuel pressure error code will confirm if it’s low fuel pressure.

Repairs

Fuel pump service will take care of any sediment build-up. The fuel line cleaning and fuel filter replacement cost around $150. A blown fuse will cost $20 to replace. Complete fuel pump replacement will cost between $300-$500 depending on the car make and model.

What Is The Battery Light?

The battery light is a part of the alternator charging system. It is connected to the ignition switch and is part of the “excitation circuit.” It is also integrated into the voltage regulator.

The voltage regulator maintains the voltage generated by the alternator and regulates how much voltage is sent out to charge the battery.

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When there is a fluctuation in the voltage being generated by the alternator or voltage charging the battery, the voltage regulator lights up the battery light or the warning lamp.

1. What Is The Use Of Battery Light?

The battery light indicates when the battery is not charging. The battery light mostly indicates that the alternator is weak or not charging the battery properly.

A weak battery does not give the battery light error and it is a very common misconception that battery light is for a weak battery.

2. What Controls The Battery Light?

The ECU controls the battery light. The ECU works in coordination with the voltage regulator.

The voltage regulator records the voltage readings and sends these readings to the ECU. Then the ECU turns on the dash light since the warning lamp is connected to the ignition switch and doesn’t need a separate power source.

Battery Light Coming On Normally

The battery light is preset to come on in certain situations. The company puts in the preset to indicate to the driver the system’s status. Let’s see what are different scenarios when it is common to see the battery light;

1. Ignition

When you turn the ignition to “on”(not turning to start), you can see various lights come on.

After you start the car, all the lights are supposed to go away. If they are still on, it could be a sign of malfunction or error in that component.

2. When the car dies

When the car stalls out or “dies”, it basically goes back on the ignition or “on,” so all the lights come back on.

What Does It Mean?

  • When the light comes on before you start the car, the ECU does a system check to ensure all the sensors and components are working.
  • When the car dies, all the lights come on, including the battery light, which is also a feature of the car. This is to show you which components are still working.
    If any specific light doesn’t come on, it could mean that a specific component is no longer working.

Battery Light Comes On While Driving

The battery light is supposed to go away when you start the car. When the battery light stays on, there could be something wrong with the car’s charging system.

The light could come on when the car is stalling out. It is most common in manual cars than in automatic cars.

The battery light can come on when excess bumps or vibrations from the road cause a loose battery terminal.

The battery light can also come on when there is corrosion or build-up on the battery terminals or the alternator terminals.

Car Shuts Off While Driving Battery Light Comes On

The battery light can also come on when there is a malfunction in the dash electronic system. You will see various dash lights come on.

What Do They Mean?

When the light comes on even after starting up, it could mean there is a malfunction in the alternator. The alternator is responsible for generating electricity to power all electrical components of the car.

The battery does not provide power to all the car’s electrical components. It is generated by the alternator and it charges the battery. Which then distributes to other electrical components.

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If the battery light comes on while your car is stalling, it could mean there is a weak alternator and the car idle is not enough to generate the required power.

A loose battery terminal can also keep the battery from charging. When the voltage regulator senses that the battery is not receiving enough charge, it sends a message to the ECU and that lights up the battery light.

If alternator terminals are loose, the insufficient charge goes toward the battery. This reduces the overall electric power being supplied to the electrical components.

The voltage regulator and ECU sense the reduction in electrical charge and light up the battery light to alert the driver of the problem.

When there is corrosion and build-up on the battery terminals, this creates resistance in battery charging, creates a load on the alternator, and creates fluctuations in the charging, causing the battery light to come on.

Sometimes there is a malfunction in the dash light circuits due to corrosion or damage, causing the dash lights to come on. The LED lights come on due to an arc jump or leak in the electrical wiring.

Conclusion

The battery light will always come on when the car shuts off and is still switched to ignition. The concerning matter is the reason why the car shuts off while driving.

The car shutting off while driving is very common in manual transmission cars since the car can easily stall if the clutch and gas aren’t controlled right.

If the car still dies while cruising or driving around then it’s better you get the car checked by a technician as soon as you can because you can never really predict or control when it will happen.

It can be very dangerous if the car shuts off while you’re on a highway far from help. It can leave you stranded and you will have to wait for help to arrive as problems concerned with this problem requires professional help in diagnosing and repairing.

Such problems can be avoided with proper maintenance because during maintenance the mechanic will check for any fluctuations in the charging voltage.

If your car shuts off while driving and the battery light comes on, then it’s nothing to be worried about because the battery light is meant to come on when the ignition switch is on.

The thing to be worried about it is why the car died while driving because that is not really meant to happen and should be taken seriously.

DrillandDriver

I’m Brian, a car fanatic, and the founder of DrillandDriver.com, I’ve been into cars my whole life. Actually, not just into them but obsessed with them. I have been working as a mechanic for over 15 years and have been deeper into the motor and electric vehicles for some years.

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