Can A Bad Starter Drain A Battery?

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this...Read more

When it comes to the functionality of the starter, it stops drawing power from the battery as soon as the engine starts.

In most cars, the starter doesn’t even run once the engine starts. A different scenario comes into play when you have a bad starter.

So, can a bad starter drain a battery?

The short answer is: yes, a bad starter can drain a car battery enough to leave it flat. If the solenoid has gone bad, it can draw too much power. Also, if you have a weak battery, the primary surge is enough to draw it to its flat line.

How Does The Starter Drain Battery?

The most important purpose a car battery serves is powering the starter. Then the starter gets the combustion engine on rotation so that you have your car on move.

How Does The Starter Drain Battery

It’s a heavy-duty motor; heavy enough to be excessive for a 12V battery. Therefore, it’s attached to a solenoid that controls how and when it starts and stops. And you control the solenoid with the ignition key.

When you rotate the ignition key, you pass the signal onto the solenoid, and the contactor plate starts the motor. Once the motor is done putting the crankshaft to the desired RPM, the solenoid then disengages the motor.

That’s how the motor draws current from the battery through the solenoid.

Here’s how everything in the starter motor terminals works:

Can A Bad Starter Drain A Battery?

Can A Bad Starter Drain A Battery

As you can now understand, the solenoid is the one that has the first contact to the battery before the motor. In most cases, if the solenoid is faulty, you may end up drawing too much current from the battery.

This draw is enough to run your battery flat. In fact, if the engine is not starting, tapping the motor and solenoid is one method to clear up the contactor plate and get it started.

How The Battery Usually Discharges

Here are the ways how a motor or the solenoid can draw charge from the battery:

How The Battery Usually Discharges

When the Car Starter Motor Engages

The engine does not start on its own. It needs the starter to reach around 2000-3000 RPM speed before working on its own. So, it needs a lot of power from the starter motor.

When the starter motor engages the battery through the solenoid, it draws a ton of power. That’s how the starter motor engages the battery and the battery discharges.

The Starter Solenoid is Drawing

As stated earlier, the motor connects to the battery and the engine flywheel with the help of the solenoid. Therefore, in order for the solenoid to work properly, it draws power from the battery as well.

Electronics in The Car

All the electronics in the car draw current from the battery when you run them. Thanks to the alternator, you never go out of charge because it’s recharging the battery on the go.

When you run the stereo, use the GPS, turn the headlights on, or run the windshield wiper, everything plays a role in the discharge process of the battery.

Parasitic Drain

There are a ton of electronics inside a modern car that keep discharging the battery, even when you have everything turned off. The clock, engine management computers, Bluetooth, Alarms, etc. keep draining the battery. That’s what parasitic drain is.

When Can the Motor Run the Battery Flat?

Your starter motor module can run your battery flat if you have the following reasons in place:

The Battery is Old

Every car battery has a life cycle to pass. If you’re using a lead acid battery, the usual life cycle will be 3 to 7 years. The life cycle for AGM batteries is longer, at 6 to 10 years. When you have used the battery up to the end days of the battery, it will discharge faster.

If the Battery is Weak

As you know, the starter motor draws too much current from the battery, if the battery has become weak, it will discharge faster. The biggest reason for car batteries to get weak is too many short trips. It doesn’t get enough time to recharge if you drive it in less than 20 minutes.

A Corroded Battery

Corrosion is one of the biggest enemies of car batteries, especially if you’re running a lead-acid battery. The sulfation or corrosion comes with bad news for a battery. It might not be able to hold the charge as much and can discharge faster as well.

Faulty Solenoid Or Motor

If you’re running on a faulty solenoid or a bad starter motor, this could result in a flat battery. With a faulty starter, it can draw current from the battery without starting the engine. The same can happen because of a bad solenoid. Either way, it can run the battery flat.

Faulty Alternator

As you may already know, the starter draws charge and the alternator recharges it. So, if you have a bad alternator, the issue might be with the alternator rather than the starter.

Bad Starter Relay

The ignition switch connects to the solenoid through a starter relay in the central ECU. If the relay goes wrong, while the solenoid and starter draw battery power, the car doesn’t start up. This way, if you attempt a few times, you eventually run the battery flat.

Bad Starter Relay

How To Know If the Starter Is Bad

If you can tell that the starter motor has gone bad, you can then easily determine which one to treat; the battery or the starter. Here are the usual signs through which you can tell if your starter is bad:

How To Know If the Starter Is Bad

Gas: If you need to push the gas pedal too much to start the engine, the starter could be bad.

Smoke: Emitting smoke while trying to start the engine is a major sign of having a bad starter motor.

Crank: If you experience too long, too slow, weak, or even no cranks while trying to start the engine, inspect the starter.

Corrosion: A corroded or worn-out solenoid or starter motor can drain your battery but won’t start the car.

Fuse: There is a fuse between the solenoid and the ignition key. If it goes bad, the solenoid won’t fire up and start the motor but draws battery power.

Output: If the engine doesn’t start, but the headlights and electronics are running well, most probably you have a bad starter.

Noise: If you hear a clicking or grinding noise while starting the engine, the starter is not functioning well.

Leaks: leaking fluid in the engine during the ignition is also a sign of having your car starter going bad.

Wires: Do you have loose wiring or binding wires around the starter motor and solenoid? Fixing them can bring a solution.

Jump starts: If you have to jump-start your battery too often while it’s not that old and didn’t drain with electronics either, the problem might be with the starter.

How To Fix An Engine Starter?

If you have a bad engine starter that is not working well and drawing excessive current, you can replace the starter.

The starter placement is different from one car to another. Look for the starter or have a look at the user’s manual of your car.

Usually, it will be under the engine which you can only access to work on by lifting the car with a jack.

How To Fix An Engine Starter

Also, you need to know the model and size of the starter. It’s okay if you don’t know that just yet. Just get a jack, and follow the steps below:

  • Put the jack under the bonnet, jack it up and put a jack stand under the car to hold it still.
  • Locate the starter module, and test the solenoid connector to see if the relay and battery are okay.
  • If these are okay, unplug the power port from the starter and the battery so that you don’t fry the battery down the line.
  • Undo all the screws that hold the starter in place. Use a torque wrench instead of an adjustable one.
  • Take the faulty starter to your nearest shop and get the exact same model of a new starter. Don’t forget to test it in the store.
  • Now, take the new starter and attach it to the place where the previous one was, and tighten up the bolts.
  • Connect the electrical wiring as well as the battery connection back on. Then you will test the car if it starts as it should.

Here’s a complete guide for you to replicate the process:

With the process above, you should now have a good starter that starts your car every time you hit the ignition.

You May Also Read: Can a Battery Drain with The Negative Cable Disconnected?

Final Advice

Getting your car fixed all by yourself is a dream DIY thing that every car owner wants to have. If you have a problem with the car while starting, it shouldn’t be as scary as it shows in the beginning.

As you can see, diagnosing a bad car starter and replacing it won’t be a big pain in your back if you do it right.

One little caution though: No matter whether the starter is under the car, or above, never forget to have your safety goggles and gloves on, before getting your hands dirty.

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this site Batteryquery to help people purchase the right battery for their vehicles. The reason behind creating this site is to help my customers purchase the right car battery who often purchase the wrong one due to their lack of knowledge.

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