Why Does My Battery Charger Needle Jump Back and Forth?

Why Does My Battery Charger Needle Jump Back and Forth?

The needle charger moving back and forth means that the battery isn’t getting the same charge consistently. The main component in a vehicle is the battery. If the battery is not working correctly, then the rest of your car will not work either. What happens with batteries is that they lose charge or stop charging effectively over time.

Not all cars have the battery charger needle on the dashboard, but it is useful because the battery gauge is essentially a voltmeter that is always connected to your battery. The tool is used to read the amount of power in your battery. The needle may move some while driving, but in reality, the needle shouldn’t move much while driving if everything is working right.

Why Shouldn’t The Battery Needle Charger Move Back and Forth?

The needle should not go back and forth since the power taken from the battery, used for the radio, headlights, and other car parts, is also given to the battery while driving through the alternator. So, the needle in the battery moving back and forth means that you have a problem with your alternator.

What Should You Check 1st? 

The alternator drive belt is the first thing to check your car’s battery needle charger jumping back and forth. The belt is used to connect the engine to the alternator, and if the belt is not working right, then the alternator won’t work right either.

If there is visible wear or damage on the belt, you better it. Changing the belt could solve all your problems with the battery needle charger moving back and forth. If the belt does not look worn out, the next thing to check is how tight it is. The belt needs to have tension to transfer the power from the engine to the alternator.

WHAT If it is The Alternator? 

The alternator takes extra mechanical power from the engine and turns it into electrical energy to recharge the battery or keep it charged.

What causes the battery charger needle to move is that the battery’s charge is changing. This can be quickly or slowly depending on the problem with the alternator and if it is cutting out and dying or something else. First, you need to test the alternator to see if it is not faulty. 

How to Test Your Alternator

The easiest way to test the alternator at home is to connect a voltmeter to the battery. The battery should read 14.4 volts with the car running without fluctuating. 

If your reading is less than this but not changing, then the battery is weak, but the issue isn’t the alternator. If the reading moves back and forth, you will need to have your alternator checked out by a professional. It could be a bad wire connection, or it could be that your alternator needs to be replaced.

Could the problem be corrosion? 

Yes, before condemning the alternators check if the wires are connected well. They might be corroded. It is essential to keep your wires neat and well connected to the battery. If your wires are corroded, clean off any corrosion and tighten down any loose wires before replacing the alternator unless you know for sure it is bad.


Now you know, though, what it means when your battery gauge jumps up and down. You know that it doesn’t mean that the battery is bad, but instead normally means that you have an issue with the alternator or even Corrosion.


Vince Dooley

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