🔌 How to Test Your Laptop AC Adapter: A DIY Guide

cits446
Aug 17
2 min read

Updated: Aug 29

Is your laptop refusing to charge? Before you panic or rush to buy a new battery, take a moment to test your AC adapter. It’s a simple process that can save you time, money, and frustration.

Safety First! First become familiar with your multimeter regarding its proper use and safety precautions.

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Testing the voltage of an AC adapter with a digital multimeter.

🧰 What You’ll Need

A digital multimeter
Your laptop’s AC adapter
A working power outlet

⚠️ Step 1: Inspect the Adapter Visually

Before diving into electrical testing, do a quick visual check:

Frayed wires or exposed metal?
Burn marks or melted plastic?
Loose connectors or bent pins?

If you spot any of these, stop using the adapter immediately—it could be a fire hazard.

📏 Step 2: Check the Output Rating

Look at the label on the adapter. You’ll see something like:

Output: 19V 3.42A

This tells you the voltage and current your multimeter should detect. Keep this number handy.

Output rating specs on an AC Adapter. The output voltage on this one is 19.5.

🔬 Step 3: Set Up Your Multimeter

Turn the dial to DC voltage (V⎓).
Set the range to 20V or higher (depending on your adapter’s rating).

🧪 Step 4: Test the Voltage

Plug the adapter into a wall outlet.
Insert the black probe into the outer barrel (negative).
Insert the red probe into the inner barrel (positive).
Read the voltage on the multimeter.

✅ What You Want to See:

A reading close to the rated output (e.g., 18.5V–19.5V for a 19V adapter).
If the reading is zero, very low, or fluctuating, the adapter may be faulty.

🛠️ Step 6: Replace If Necessary

If your adapter fails the test:

Replace it with an OEM (original equipment manufacturer) adapter (avoid cheap knockoffs).
Match the voltage, amperage, and connector type exactly.

Final Thoughts

Testing your laptop’s AC adapter is quick and easy—and it can help you avoid unnecessary repairs. With just a multimeter and a few minutes, you’ll know whether your power supply is the hero or the villain in your charging saga.