Alternator Overcharging: What Causes It?

Alternator Overcharging: What Causes It?


April 12, 2022

The alternator is a crucial component in the car’s operation. Undercharging is more typical, but it’s also feasible for the alternator overcharging resulting in a chain of electrical issues.

If your vehicle’s alternator is damaged or worn, the result can be an overcharge, which might cause it to fail. The only option is to have it rebuilt or replaced.

How Does An Alternator Work?

How Does An Alternator Work

The engine’s two electric sources are the alternator and battery.

The battery stores a significant amount of electricity that may be used to operate electrical gadgets after the engine has been shut off, such as the radio or hazards, but its major purpose is to deliver a big burst of power to the starter and get the machine moving.

When the engine starts, the alternator takes over as the main power source. It also recharges the battery so it can start up again. A drive belt links the crankshaft pulley and the alternator pulley to allow energy from the engine to be transmitted to the alternator.

An alternator is a machine that converts rotational energy into electrical power in simple terms.

The Symptoms Of An Alternator Overcharging

Alternator Overcharging: What Causes It?

The battery dashboard warning light is the first indication that the alternator is failing.

To determine and confirm whether the alternator is at fault, use an OBD2 scanner. If you didn’t have a scanner, you’d have to take your automobile to a mechanic, and see how much it cost.

With the exception of brake lights and turn signals, every component of your car will be next. The light bulbs will last longer if they are variable and high voltage because of their greater resistance.

The high voltage will, in more severe circumstances, cause the battery to overheat and degrade in performance. Fuses and relays are also common since they provide safety by preventing greater electrical damage.

Alternator Overcharging: What To Look For?

The battery voltage is set at 12.6 volts whereas the optimum alternator voltage is 14.2 volts.

The battery voltage is set at 12.6 volts, whereas the optimum alternator voltage is 14.2 volts.

It’s simple to tell whether your automobile’s alternator overcharging it with these figures and a multimeter.

Stage-Wise Instructions

  1. Arrange the multimeter to 20 volts DC. 
  2. Attach the negative probe to the negative battery clamp, then join it to the positive.
  3. If the battery is dead, the first reading should be at least 12.6 volts and most likely above 12.2 volts after turning off the engine.
  4. Turn the key to “On” and start the engine. As the alternator begins to charge the battery, it should be between 14.2 and 14.7 volts.
  5. Turn on the radio, headlights, and risks. The reading should still be loftier than the starting battery voltage, which is frequently around 14 volts.

If the car is left off for an extended period of time e.g half an hour, the battery voltage should be greater than 12.2 volts. When the battery’s voltage falls below 12.2 volts during transit, it’s dead.

For at least 30 minutes after that, keep driving to see what caused the low battery voltage.

The alternator generates a voltage of 14.2 to 14.7 volts. This is adequate wattage to charge the battery fast but securely. When you turn on the headlights or other electrical devices, the voltage will drop somewhat as the alternator must also power those gadgets.

It’s critical to check the alternator voltage whether or not you’re having trouble with your battery.

If the voltage drops beneath 14.2 volts without load, or 12.7 volts under load, it indicates that the alternator isn’t producing adequate power. If the alternator can still deliver enough current despite this.

When you first start your car, the voltage reading will be greater than 14.7 volts. Because the voltage reading when the engine is running is higher than 14.7 volts, the overcharge is most apparent.

Despite this, there isn’t a simple solution to the problem addressed in this instructions.

How To Repair An Alternator Overcharging? 

How To Repair An Alternator Overcharging

I’ve arrived across a few short-term bypass methods, but I don’t suggest them. The problem must be dealt with correctly, and the only option for repairing or replacing an alternator overcharging is to take it out and send it away.

To repair it, you’ll need to unlock the alternator and have extensive knowledge of electrical systems, which is well beyond the skill of a do-it-yourself mechanic.

Instead, we may turn to one of several alternator repair firms or purchase a new alternator from Amazon or a regional parts store.

The alternator’s position influences how hard the work is. The job is simple if the device is accessible; but if it’s hidden away in a hidden place, you’ll have to deal with obstacles that get in your way.

In this case, I’d recommend consulting a car-specific guide because it will show you how to get to the alternator.

Here’s A List Of The Equipment You’ll Need

Alternator Overcharging: What Causes It?
  • DEWALT Mechanics Tool Set
  • Permatex 80078 Anti-Seize Lubricant
  • Klein Tools Cabinet Tip Screwdriver
  • Lavaxon Wire Brush Set, Stainless Steel Bristles with Curved Handle Grip for Scrubbing
  • Powermaster 47861 Alternator

Step By Step Pedagogy

  1. Remove the negative terminal from the battery.
  2. Remove any components that are in the way to make room for your alternator. It is critical not to remove the coolant hoses since this will add a significant amount of time.
  3. Remove the serpentine belt tensioner and remove the serpentine belt from the alternator pulley.
  4. Remove the alternator from the vehicle. Remove the alternator screws with a socket and large ratchet.
  5. To improve the connection, With a wire brush, clean the alternator bracket and bolts.
  6. Slide the alternator into place on the bracket. Anti-seize should be applied to the bolt threads and inserted into the alternator holes.
  7. By hand Tighten the bolts in a circular motion, alternating between them to ensure an equal drop. Finish with the ratchet.
  8. Connect the alternator cables in reverse order.
  9. Remove the serpentine belt, replace it, and double-check that each of the pulleys is seated correctly. Check out the engine bay sticker or the repair manual for more information.
  10. Make sure the battery is plugged in securely, then reconnect the negative terminal.


Is It Legal To Drive With An Alternator Overcharging?

An alternator overcharging raises the risk of electrical components such as light bulbs being destroyed, as well as the battery.

You don’t have to call a tow truck right away, but you should not drive your automobile normally. Take it to a mechanic or repair it yourself using the information supplied if possible.  

Is It Feasible For An Alternator To Output 15 Volts Or More?

The battery’s recommended charging rate is typically 16 to 20 amps, while the alternator voltage should be between 14.2 and 14.8 volts.

The manufacturing company specifies this level, however, it depends on your needs. Because European automobiles must operate with daytime managing lights or basic low beams at all times, the alternator voltage may be set higher.

In Such A Case, Is It Necessary To Change The Alternator?

I will try to make a point of about 15 volts in an average scenario, but 18 volts is far too much and may cause the battery to overheat. If your alternator is putting out more than 15 volts, you must replace or change it as soon as possible.

How Do I Prevent My Automobile Battery From Being Overcharged?

Because the wrong voltage regulator on the alternator prevents the overcharge, the battery won’t charge on its own. When you replace the alternator overcharging will be prevented.

Is It Conceivable For An Alternator Overcharging As A Result Of A Flawed Ground?

The alternator’s ability to overcharge is debatable. The difficulty is more likely to result in undercharging rather than alternator overcharging since power is lost along the route to the battery.

The voltage regulator keeps the alternator at a constant of 14.2 to 14.7 volts on the battery terminals, with the most important role of ensuring that the voltage does not go over as demonstrated by multimeter readings.

Are 14.7 Volts Too Strong?

According to my study, a healthy alternator’s upper output limit is 14.7 volts. Anything above 14.7 volts is cause for worry because it will result in light bulb failure and battery damage.

What Is The Distinction Between A 12v And A 14v Alternator?

Both the 12-volt and 12.6-volt batteries are said to be “charged,” and there’s no difference between them. A 12-volt alternator must produce at least 14 volts in order for the battery to be adequately charged.

Anything less, and the battery won’t be charged fast enough, eventually depleting as a result of all of

Is It Possible For A Faulty Alternator To Make The Belt Squeal?

Yes, a defective alternator pulley will make the belt squeal, especially if the engine has just been started.

Is It Permissible To Keep The Car Battery Charged Overnight?

Yes, it’s fine to leave the battery on the charger overnight. I’m not sure what all the fuss is about – once the battery has a voltage of 12 volts, the charger understands it doesn’t need to be charged anymore. 

It’s like saying that you shouldn’t drive after dark because the alternator will continue to supply 14 volts to the battery and overcharge it. Simply double-check whether your charger has an automatic shut-off feature, allowing you to alternator overcharging overnight without issues.

Is It True That A Car Alternator Will Charge At Idle?

Yes, the battery is fully charged when operating at a low speed. The older dynamo alternators required higher RPM to deliver ample current – modern alternators provide the same amount of power at all RPMs.

Is It True That Driving A Vehicle Recharges The Battery?

Yes, because you’re in control of the car, the alternator is charging the battery. After starting, it takes around 30 minutes to fully charge a battery.

When Charging, Do I Need To Unplug Both Battery Terminals?

It’s debatable whether or not to unplug the terminals before charging, but I’d rather be safe than sorry and do it first. Varta battery makers advise removing them as quickly as possible because a minute is all that is required.

How Much Voltage Does A Battery Lose Over The Course Of One Night?

In general, don’t anticipate any major drops – even 0.1 volts might be too much. Consider the following scenario: if the minimum voltage to start the car is 11.8 volts and the optimum battery voltage is 12.2-12.8 volts, a single week of inactivity will leave the battery with enough juice to not fire up

If you measure a voltage drop over the course of one night, it’s because there is an issue in the system that has to be addressed.

We all know that automobiles may be parked for a long time and still function well; as a result, if you observe a voltage drop, it implies an electrical trough in the procedure that needs to be handled.


If you have an old or faulty alternator, it might overcharge your automobile’s electrical system, resulting in serious damage.

This problem may be resolved in less than an hour if you have the right socket set and a substitute alternator. If it is inexpensive, visit a local refurbishing store or buy a new one.

Try the best one and see that changing an alternator is not difficult, but it does require some knowledge. The basic labor cost of changing an alternator is about $200, but you may save money by purchasing the tools and keeping them on hand for future work.

You’ll slowly build your toolkit up until virtually every repair necessitates only replacement items, greatly lowering the overall cost.


Jeffrey Bryce is an experienced motorcycle rider with years of experience caring for motorcycles. His natural fondness for motorcycles have made him come up with, which is dedicated to answering and teaching you how to care for your bike with the care it requires. LetsGoForARide is the one of his important lifework in reaching out to communities of motorcycle enthusiasts on how to take care of their bike and choosing the correct spare part.