How to Test an AC Adapter with a Volt/Multi-Meter

If your laptop is no longer receiving a charge, or is only intermittently receiving a charge, there are a few different components that could be the cause. The AC adapter is a likely culprit, but it can be difficult to determine if a fault DC jack or another component could be causing the problem instead. By testing your AC adapter with a multi-meter or volt meter, you can determine if it is outputting power and eliminate the possibility of a failed AC adapter. Here is how to test the AC adapter and determine if it needs repaired.

  1. Turn off the laptop if necessary and unplug the AC adapter from the laptop. Leave the adapter plugged into the wall outlet.
  2. Read the rating on the side of the AC adapter to find out its intended voltage. For example, the “Output” listing may say something like “9V DC”. This means the adapter output 9 volts of DC power.
  3. Set the multi-meter to DC and set the range to something slightly higher than the expected output voltage. For example, if the adapter is rated for 9 volts, set the range to 20 volts.
  4. Connect the leads to the ports in the multi-meter if they are not already connected.
  5. Stick the red lead inside the tip of the AC adapter and press the black lead against the metal around the outside of the tip. Keep both in place at the same time. The meter should read something near the rated voltage on the AC adapter. Some adapters output a much higher voltage than their rating, but it should be within a range of around 30% up or down.

If you get a rating that is somewhat higher or lower, the adapter is still likely functioning correctly. If you get no rating at all, or the voltage seems to be intermittent, your AC adapter may be damaged and should probably be replaced.

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