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How To Fix High Battery Voltage

Your car isn’t working properly and you suspect that it’s because of a high battery voltage. But how can you fix this problem? We researched and consulted with different industry experts regarding this concern, and here’s what we found.

First, find the reason why your car’s battery is experiencing a high-voltage reading. Next, use the appropriate method to fix the issue from its source.

Take note that the DIY solution to use to restore your vehicle’s battery’s voltage often depends on the primary cause of the issue. So continue reading as we talk about these possible reasons in greater detail. We’ll also tackle some potential solutions you may use to fix your car’s battery problem.

Before you continue reading, let us say we hope you find the links here useful. If you purchase something through a link on this page, we may get a commission, so thank you!

4 Reasons Why Car Battery Voltage Is High

Checking voltage with multimeter and charging car battery with charger from home electricity.

Before trying to fix your vehicle’s high battery voltage, it’s important to know why the problem occurred. Take note that this issue may appear because of different reasons:

Loose Electrical Connections

Take note that many vehicles run on electricity. This power comes from different intricate assemblies, components, and systems to power different features, such as the AC and headlights.

However, loose connections may disrupt this flow of electricity. The result is an improper charge delivery from the battery, creating a high battery voltage.

Faulty Alternator

The alternator is an assembly that converts mechanical energy into electrical energy. It should also help turn the drive belt, providing sufficient power and voltage to connected systems.

But a bad alternator may distribute power incorrectly, resulting in a high battery voltage. You may diagnose if the alternator is at fault for the increase in battery voltage by watching out for certain symptoms. Some signs to look out for are:

  • Persistent dashboard warning light
  • Headlights dimming or flickering
  • Strange sounds or smells coming from under the hood
  • Poor overall car performance

At this point, you can read our post on how much voltage is too much from an alternator to gain additional insight into this particular topic.

Bad Starter

As its name implies, the starter is a component that helps engage the engine’s flywheel. If it’s in good working condition, the starter should help the engine’s cylinders capture the correct amount of air and fuel, helping the vehicle’s engine turn over.

Also, take note that the alternator generally influences the battery’s performance. So a malfunction from the starter may also cause the battery to produce a higher voltage than normal.

Other symptoms of a bad starter to watch out for are:

  • Overheating engine
  • The car has difficulty starting if it's able to engage at all
  • Clunking, grinding, or whirring noises from under the hood

Poor-Quality Battery

Perhaps the car battery is the primary suspect to it exhibiting a high voltage. Take note that it should work by bringing power to your vehicle’s different assemblies and systems. Plus, the charge provided by the battery should be correct to allow the engine to ignite.

You may know that the battery is at fault for the higher-than-usual voltage if it promotes other issues like:

  • Engine finds it difficult to turn over
  • The car shuts down after running for a few minutes
  • Dimming lights (e.g., headlights and dashboard lights)

How Do You Trace A Short Circuit In Your Car?

It's important to mention that finding an open or short circuit in your vehicle may require sufficient automotive and electrical understanding. If you believe that you're finding it more challenging than expected to search for the fault, request the help of a reliable industry expert.

Still, if you wish to continue searching for and fixing a short circuit in your vehicle, you typically need to know and abide by certain precautions. Some preventive measures are:

  • Study the electrical diagram of your vehicle to see how its circuit should work.
  • Disconnect the negative battery cable from its terminal to prevent an electrical circuit from running through the vehicle during the troubleshooting session.
  • Be careful when probing connectors as you don’t want to bring additional harm to those components.

After understanding those points, you can continue the troubleshooting and repair of a possible loose connection in your car by following these steps:

What You’ll Need

  • Short circuit detector
  • Needle-nose pliers
  • Voltmeter or multi-meter

Step-By-Step Guide

  1. Turn off your vehicle’s engine and engage its parking or emergency brake.
  2. Open the hood when it’s safe to touch.
  3. Disconnect the battery cables from their terminals, starting with the negative cable.
  4. Search and open the fuse box of your vehicle.
  5. Pull out a fuse and connect the short circuit detector to the battery.
  6. Connect the detector's probe to the fuse’s terminal.
  7. Turn on the detector and follow the LED and/or beeping noises from the detector to search for the open or short circuit.
  8. If you can’t find a fault, return the fuse to its original location. Then, repeat steps 5 to 7 for another fuse until you can find the bad circuit or loose connection.
  9. Secure the loose connection once found.
  10. Remove the short circuit detector from the battery.
  11. Return the battery’s cables to their proper terminals, starting with the positive cable.
  12. Test the battery’s voltage if it’s now normal.

Check out this car short circuit finder on Amazon.

You can also check out this video for a visual guide to the steps mentioned above:

How To Fix A Car Starter?

Replace the parts of the starter motor of the old car

Repairing a car’s starter generally means that you should replace it with a new unit. However, completing this task may also potentially eliminate the high voltage encountered by the vehicle’s battery.

Make sure to protect yourself for this job by wearing protective goggles and gloves. You can then follow these general steps once you’re ready:

What You’ll Need

  • Wheel chocks
  • Floor jack
  • Jack stands
  • Ratchet and socket
  • Voltmeter or multi-meter
  • Replacement starter

Step-By-Step Guide

  1. Turn off your vehicle’s engine and engage its hand, parking, or emergency brake.
  2. Chock the wheels.
  3. Wait for the engine to cool before opening the hood.
  4. Disconnect the negative battery cable from its terminal.
  5. Lift the front of the vehicle with the floor jack. Install jack stands to help support the vehicle’s frame afterward.
  6. Find the starter underneath the engine block.
  7. Loosen the bolts securing the starter assembly and remove them.
  8. Disconnect the cables attached to the starter assembly.
  9. Install the new starter in the same location as the old unit. Make sure to pay attention to the unit's orientation.
  10. Secure the new starter assembly and lower the vehicle to the ground.
  11. Reconnect the negative battery cable to its terminal.
  12. Check if the battery still produces a high voltage or if its power readings are now normal.

Check out this replacement starter on Amazon.

Note: Some of the steps highlighted in this procedure may not apply to your vehicle’s specific model. Consult the owner’s manual or ask the vehicle manufacturer’s customer service hotline if you need help with any part of this process.

Watch this video if you want to check out a visual representation of this procedure:

You might also be curious about learning how to fix a starter without replacing it. If so, follow that link to know the process.

What Is The Normal Battery Voltage When Car Is Running?

car on the road, How To Fix High Battery Voltage

The typical car battery should have a voltage reading of 12.6 volts while the engine is off and the battery has a full charge. But the batter’s voltage usually rises to about 13.5 to 14.5 volts while the engine is running. Voltage readings higher than 14.5 volts puts the vehicle at risk of experiencing numerous issues.

What Happens If My Car Battery Voltage Is Too High?

Car starter battery voltage measured with multimeter in a repair garage

Watch out for certain symptoms to identify if your car’s battery has a high-than-usual voltage reading. Some possible signs that may surface include:

  • The battery is hot even after putting the car at rest
  • Visible deformation to the battery’s housing, especially on its sides
  • Frequent drop in battery fluid level
  • Opening the hood greets you with an acid-like stench

What Voltage Is Too Low For Car Battery?

Mechanic test car electric system with multimeter, check car battery voltage.

A battery voltage is too low if it reads 12.4 volts or under. The risks of your car battery dying will be higher as its voltage reading drops lower. At 11.9 volts, expect the battery to have insufficient power to allow the vehicle’s engine to turn over.

Final Thoughts

Avoid running your car for extended periods as soon as you notice the signs that its battery voltage is higher than normal. Once you park the vehicle in a safe spot, troubleshoot it to find the source of the problem. You can then use the appropriate DIY solution based on your findings or request help from trustworthy industry professionals.