How to Check for a Draw on a Car Battery With a Test Light

How to Check for a Draw on a Car Battery With a Test Light?

Your car faces difficulties while starting? It is mostly because of constant battery drain. Isn’t that a frustrating experience? It’s also a hassle when your car battery drains, even when the vehicle isn’t turned on.  

How do you check for a draw on a car battery with a test light? A few simple steps only. Gather the necessary tools and disconnect the battery terminal that is negative. Now, connect one test light end to the negative terminal and the other end to the disconnected negative cable. However, do not forget to follow necessary safety precautions. 

In this study, you’ll get the in-depth steps on how to check battery draw with test lights. I’ll also discuss why test lights are preferred in this checking as well. 

How to Check for a Draw on a Car Battery With a Test Light? Symptoms And Steps You Need to Know

Before going to know the steps, you should know first what are the symptoms of a battery drain, right? Let’s get to know when you have to check the battery draw. The symptoms, in a nutshell, are as follows: 

  • Difficulty in start
  • The car battery doesn’t hold the charge for a long time
  • Dim interior and dashboard light

Now you know the symptoms. Let’s get into the steps now. 

How to Check for a Draw on a Car Battery With a Test Light

Step 1: Manage Necessary Tools

Manage the following tools for the battery check. 

  • A digital multimeter
  • A test light
  • Safety goggles and gloves
  • Wrench or pliers

In addition, you may keep a pen and a piece of paper to write readings if you think you should use them for memorization. 

Step 2: Turn Off All Electrical Accessories

Ensure all the vehicle’s lights, radios, and air conditioning systems are turned off. In addition, the ignition has to be in the off position. Consider it a safety measure that should be valued highly. 

Step 3: Disconnect the Battery Terminal 

Disconnect the negative battery cable from the negative battery terminal using the wrench or plier. Doing this will basically isolate the battery cable from the vehicle’s electrical system. You’ll find a negative (-) sign where the negative terminal is situated. 

Step 4: Connect the Test Light

Now, you have to connect the test light. It’s very simple. Connect one end of the test light to the negative terminal and the other end to the negative battery cable. After connecting the test light, carefully notice what the outputs are. 

If the light illuminates, that means your battery is draining. If not, then the battery might be fine. The problem might be from somewhere else. 

Note: If the lights illuminate dimly, then you should not be worried too much. This means the battery drain incident isn’t severe. But if it illuminates heavily, battery drainage is a matter of concern now.

Read:  Why Is the Battery Light On After Replacing Alternator?

4 Core Causes Why Car Battery Drains

Well, car batteries might be drained due to a variety of reasons. Some of the core reasons are as follows: 

  1. Damaged Alternator: Basically, if your car battery isn’t charged appropriately, your car won’t start, or your car might struggle while starting. It will cause electricity fluctuation and car battery drain as a consequence. Replacing the alternator will resolve the battery drain issues. 
  2. Parasitic draw: It’s basically if you leave the car carelessly. For instance, you forget to switch off the radio, lights, and gloves box completely. While you’re moving with your car, it’s fine if your radio is working or your headlight is on. 

    But, if the car is turned off, the battery isn’t charging, and your vehicle’s electronic components are still running, it will cause battery drain. 
  1. Loose Battery Connection: A loose battery connection might cause starting difficulty. It’s because the battery is drained and can’t transmit power properly. Or failed to transmit power as it is completely drained. Contact a mechanic to resolve the connection issues. 
  2. Battery Age Does Matter: Sometimes, it may be the age of the battery. If a car battery is old, it might fail to transmit power adequately. If your vehicle is off, even just start, now is the time to change the battery. 

A battery might work for 5 – 8 years, depending on the car’s maintenance and other environmental factors. Extreme cold weather can also affect the battery condition and might drain as well.

What to Do If the Battery Drains?

What to Do If the Battery Drains

In this case, changing the car battery might be the best solution. To do so, you’re required to follow a few simple steps. 

  • Disconnect the battery cables first. Start with the negative terminal, followed by the positive one. 
  • Now, remove the screws or fasteners that hold the battery. Do not forget to have a look at the battery tray. You may find a lot of mold dirt as guests there. Clean the tray. 
  • Now, put the new battery into its place with the fasteners or screws the previous battery was being held.
  • After doing all this, recheck the battery terminal following the steps mentioned above. Hope your problems are solved.

Preventative Measures For Car Battery Drain

Preventative Measures For Car Battery Drain

Here are the preventative measures for car battery drainage. 

  • Keep an eye on your battery’s overall condition. Check for any signs of corrosion, loose connections, or damaged cables. Clean the battery terminals and apply a thin coat of petroleum jelly to prevent corrosion.
  • Try to drive your vehicle regularly, or at least in a timely manner. Driving cars allow the alternators to charge the battery properly. 
  • Turn off additional electronic accessories. For instance, headlights, radio, air conditioning, and interior lights
  • If you install aftermarket stuff in your car, consider unplugging these while the car is turned off. These devices can cause battery power draw. 
  • Parasitic draining should also be checked. Take a multimeter to check how much current exceeds 50 milliamps; parasite drainage issues must be fixed by a professional.
  • Keep your battery clean and secure. Make sure the tray, or whatever the battery is staying, is free of dirt and debris. This could cause performance fluctuation. 
  • A malfunctioning charging system can cause battery draw. Regularly check the alternator, voltage regulator, and associated wirings.
Read:  Battery Light On In Car: Possible Reasons And Solutions
If you’ve successfully checked for a draw on your car battery using a test light, it’s essential to consider other factors that might affect your vehicle’s electrical system. One such factor could be a fuse issue that could cause the battery light to come on. To understand more about this, you can read our article on can a fuse cause the battery light to come on. Additionally, if you’re dealing with a key fob battery low warning light issue, our guide on key fob battery low warning light can provide valuable insights into resolving it.


Here are some additional questions that help sharpen your knowledge. 

Q: How much does it cost to replace a car battery?

In general, it might cost between $50 and $300, depending on the model and type of vehicle. If the problem is a faulty alternator or the car battery connection, fixing the particular problem is cheaper and convenient. But, for other causes, battery replacement is required.

Q: Is there any safety outfit while checking the car battery draw?

No. However, it is suggested to wear goggles and gloves while performing the battery check with a test light.

Bottom Line

If your car seems to be facing difficulties while starting or shows dashboard lights, assume there’s a battery draw in your car. Perform the battery check with the test light because it’s easy. After applying all the necessary steps, you will be confirmed that there’s a battery draw. 

Decide if replacing the battery or diagnosing the problem and performing a recovery solution is cheaper. It’s up to you. Follow the necessary precautions for preventing battery drainage in your car. 

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