Car Batteries

What Does It Mean When Battery Gauge Goes Up And Down?

Mike Cross
Updated Oct 17, 2020

A key component in any vehicle is the battery. If the battery is not working right, then the rest of your car will not work right either. The main problem that happens with batteries is that they lose charge or stop charging effectively over time.

As batteries age, they struggle with holding a charge. Some vehicles have a battery gauge on the dash and sometimes the needle jumps around.

Does the needle jumping mean your battery is bad? Well, read on to find out the answer to that question and to find out what it really means when your battery gauge goes up and down.

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What Does It Mean When Battery Gauge Goes Up And Down?

Battery Gauge

Before going into detail about what it means when your battery gauge jumps around, we will first talk about what the battery gauge on your dash actually is.

Not all cars have the battery gauge on the dash, but it is a useful thing to have because the battery gauge is essentially a voltmeter that is always connected to your battery.

A voltmeter is a tool used to get the reading of how much power is 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.

That is why it is a concern when it does jump around while driving.

Why Shouldn’t Battery Gauge Goes Up And Down?

You may be wondering to yourself why the needle shouldn’t move while driving. You may be thinking there is power being taken from the battery by the radio, headlights, and other parts of the car while driving, so shouldn’t that make the needle go down?

Well, this is true that power is being taken from the battery, but power is also being given to the battery while driving. That is the purpose of the alternator.

So, does the needle in the battery gauge jumping around means the battery is bad. No, it actually typically means that you have a problem with your alternator.

Alternator Problem

Your alternator is responsible for taking extra mechanical power from the engine and turning it into electrical energy to recharge the battery or keep it charged. Using best battery tender to do that is excellent decision.

The needle jumping means that the battery isn’t getting the same amount of charge consistently.

The reason the needle jumping doesn’t mean that the battery is bad is that if you have a battery not holding a charge that will only cause the needle to not go up as high on the gauge, but it won’t cause the gauge to jump.

What causes the gauge to jump is that the charge of the battery is changing and this can be quickly or slowly depending on the problem with the alternator and if it is cutting out and dying or something else.

The first thing to Check

The first thing to check when you have your cars battery gauge jumping around is the serpentine or alternator drive belt. The belt is what connects the engine to the alternator, and if the belt is not working right then, the alternator won’t work right either.

When checking the belt you want to check two things. Those two things are the wear on the belt and also its tightness. If the belt is starting to look old, then that can cause the tension to change while driving.

If you see any visible damage or wear on the belt, then it is a good idea to change it. Changing the belt could solve all your problems with the battery gauge jumping.

If the belt does not look wore out, then the next thing to check is how tight it is. The belt needs tension to be able to transfer the power from the engine to the alternator.

It does this by spinning along with the engine and turning a wheel on the alternator. If the belt is loose, then it may slip and this will cause the alternator wheel not to spin and will, therefore, cause the alternator not to work.

You want to make sure the belt is tight, so all the parts will spin. However, you don’t want to tighten it over because this can make it hard to spin for the opposite reason. Also, having the belt too tight can lead to it breaking or wearing out sooner.

Testing Alternator

Battery Gauge Goes Up And Down
The easiest way to test the alternator at home is to connect a voltmeter to the battery

If the belt seems fine and it is the correct tightness, but you are still having issues with the battery gauge jumping, then you will have to test the alternator.

The easiest way to test the alternator at home is to connect a voltmeter to the battery. The battery should read around 14.4 volts with the car running and not fluctuate.

If it is reading less than this, but not changing, then the battery is weak, but the issue isn’t the alternator.

If the reading is jumping, then you will need to have your alternator checked out by a professional because it isn’t working right. It could be as simple as a bad wire or connection, or it could be that your alternator needs replaced.

Corrosion

Before condemning the alternator though, one other thing that can cause the battery gauge to go up and down is if the wires aren’t connected well or are corroded.

It is important to keep your wires clean and connected tightly to the battery. Clean off any corrosion and tighten down any loose wires before replacing the alternator unless you know for sure it is bad.

Bad connections can cause reading spikes, and it is a lot cheaper to clean and tighten wires than to replace the alternator

Conclusion

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.

You should understand better why that is the case and you also know some things to check and ways to fix the problem. You know to check all the wire connections and clean any corrosion.

You also know to check the alternator belt and replace if worn or make sure it is tightened correctly. Lastly, if neither of these things solves the problem then you know to test the alternator and replace it if bad.

Your battery is key to driving your car, so you want to make sure it is charging right before you get stranded somewhere and if you notice your battery gauge jumping, then you should have things taken care of right away.

Mike Cross
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14 comments on “What Does It Mean When Battery Gauge Goes Up And Down?”

  1. Battery gage moves while driving or at a stop what can it be we already replaced the battery and alternator even with ac is on it goes to 9 I was told it suppose to stay at 14 and not move can someone help me out by telling me what maybe the problem it’s never happened before it’s the first time going in 4 days

  2. Having same problems. Gauge dropping from 13 steadily down to 0 . Changed the battery. Then the alternator was changed. Same issue .
    Now why?

    1. Haha, my 2012 Nissan Frontier 4x4 crew cab does the exact same thing. This is the 3rd alternator and 2nd battery new drive belt and tensioner and the voltage drops so low the truck stalls. New coilpacks and spark plugs and that didn't solve the problem either!

      1. Check the connection where the alt plugs in..I've seen where oil and grime get in there and cause alt to die out quick

    2. Could be that one of the ground wires need to be tightened. Check all ground wires to ensure that they are tight. Also check the one wire on the alternator that sends the current to the gauge or charge indicator light.

  3. I'm experiencing the same problem.Mine only happens when driving.Slowing down or turning the gauge goes down if i speedup gauge goes way up but at a constant speed im fine.Idle with headlights and AC running the gauge is perfect.

  4. 1996 S-10 2.4L V-4 battery got drain I pushed and stars my truck, thanks God that is standard then I took the Battery for a bench test which one passed the battery was good then the alternador was replaced but the voltage indicator needle on the dash was down in 0-voltages. Help..help what could be done in this situation....Thanks in advanced

  5. I have had the same problem with my 09 Chevy truck I put a new battery on and Alternator and it still does the same what is causing this problem can anyone tell me

  6. I worked on two different gm cars that went through several alternators far too fast. I found the heavy gauge positive cable from the battery to the starter motor was being pinched intermittently by the chassis either by bouncing or turning the car. This dead short is not fuse protected and causes catostrophic trauma on the alternator. Once found, it was a simple and permanent fix.

    1. Some alternators have a single wire that sends power to the gauge or battery indicating the charge ( when light is out) then current is good. When the battery indicating lamp is lit then your battery is not getting the charge. If that single wire is loose or broken then the light will be on and you can possibly have the flickering light or jumping needle on your gauge.

  7. My 74 'vette has what appears to be the same problem as many of the above listed when it comes to spiking alternator gauges. After picking it up from the mechanic the amperage gauge jumped like crazy, but never reached the high number-age for volts [10-14 amps] and stay's in that range once the motor is up and running. Next I I found the wire off the back of the alternator was not very well tightened, so I tightened it, but the gauge still spiked, but on the low end Next, I found the wire that led inside to the foot area and the right hand side door light comes on once door is open and off when shut. Please advise me as to what I should do next. Thank you

  8. I have a 2009chevery silverado and the battery gage goes from 14 to 12 and it keeps going down what can make it do that and my lights go dim at night

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