How to Tell if Alternator is Draining Battery (4 Methods)

How to Tell if Alternator is Draining Battery

The major responsibility of an alternator is to recharge the battery while the car is being driven and is expected to last as long as a vehicle. Alternators are an integral part of a vehicle without which the car’s battery will not recharge.

Over time, some components of the alternator may get damaged resulting in its inability to charge the battery. In some cases, battery drainage has also been attributed to a bad alternator but this is said to be in rare cases.

Since one does not often see battery drainage as a result of a bad alternator, how can you tell if the alternator is draining the battery?

To check if the alternator is draining the battery, you should check for signs such as the inability to start the car, dim interior lights, etc. You can also take the car to the mechanic/repair shop for them to confirm if your alternator is draining your battery.

Can an Alternator Drain a Car Battery?

An alternator can drain a car battery although this happens on rare occasions. The alternator is responsible for converting an engine’s energy while rotating into an electrical charge, simply put it produces per that charges a battery.

For a car battery to drain as a result of the alternator, something must be wrong with some components of the alternator or its connection. There is no way the battery will charge if some components of the alternator are faulty, rather it will drain out.

A battery draining as a result of the alternator may not be direct, it could be indirect from other devices in the vehicle that generates power from the battery.

How to Tell if Alternator is Draining Battery

Dealing with a drain-out battery is not uncommon, it could be a result of a problem with some parts of the engine, a faulty/bad alternator inclusive. It is very possible to detect if your battery is draining because of the alternator before it dies completely.

Here are some signs you should look out for:

Clicking Sound When Starting the Car

Although this can be attributed to other problems in the car such as a bad starter, but if the starter is good, it could also mean the battery is draining and near death because of a bad alternator.

When the alternator is bad and draining the car battery you will have difficulty and a most likely a clicking sound when starting the car.

Dim Interior Light or Very Bright Headlights

The battery also powers other accessories in the car like the interior light and headlights, if the alternator is draining the battery you should be able to tell by the brightness of the interior light when the car is running.

If the headlight also runs brighter when you accelerate and dims as you stop, it is often caused when the alternator is not keeping the battery charged.

Run a Test on the Alternator

This is often done by running the engine while the negative battery cable is disconnected. This method may prove effective but in the long run, causes damage to the vehicle’s electrical system.

Consult a Mechanic

As a last resort, you may need to have a mechanic take a look at the engine and alternator in order to determine if the alternator is draining your battery.

What to do if Alternator is Draining Battery

It has been established that if the alternator isn’t working then there is a problem with some of its components or the connection. After it must have been determined that the alternator is the cause of the draining battery, you should do the following

1. Check and Fix Wiring Problems

One reason why an alternator may not charge the battery is a result of faulty connections and wiring. If any of these wires are not attached properly or become detached, the alternator will not work.

One of the many things that should be done is to fix the wires and ensure they are properly connected.

2. Replace Worn Out Belts

The belt and pulley system helps the alternator in its power generation process, overtime this belt can snap or break and becomes useless.

A broken belt needs to be replaced, the same applies to the pulley. If the belt or pulley is damaged the alternator won’t be able to charge the battery.

3. Have the Fuse Replaced

Replacing a fuse will only be possible in vehicles that have a fuse for the alternator. For vehicles that have a fuse, you will need to replace the fuse before the alternator can work.

If you are confused as to whether your vehicle alternator has a fuse, you should check the diagram of your vehicle’s fuse box

4. Ensure the Vehicle’s Computer System is Functional

Just like some other parts of an engine, the alternator is also controlled by the computer system. If the car’s computer system isn’t working well, it will definitely prevent the alternator from charging the battery, therefore, you should ensure the computer system is functional and have an expert check it if need be.

Tips for Preserving your Car Alternator

Although alternators are meant to last almost the life span of a vehicle, if not properly preserved, they will get damaged earlier than they should.

In order to keep the alternator working for much longer, you should consider using some of the following tips;

  • Regular Maintenance: One known way of preserving a car’s alternator is doing routine maintenance with attention to the alternator and other parts of the engine. With regular maintenance, you will be able to quickly detect if there is a problem with the alternator.
  • Keep the Alternator Clean: With use over time, the alternator can get dirt and dust on it thereby preventing air from getting in, you definitely do not want the dirt getting inside the alternator because it will cause damage to it. In order to prevent dirt from getting inside the alternator, you should clean it out as often as possible.
  • Keeping the Pulley in Alignment: The pulley can get out of alignment as a result of jostling from driving. It is important to constantly keep the pulley and alternator in alignment for it to work well. Misalignment could also be because of wear and tear in which case you will have to replace it.


In trying to detect why your battery is draining, it is important to be careful so as not to cause more damage to other parts of the engine and also consult a professional if need be.