How to Check if your Laptop Power Supply is Faulty or Failing

Sometimes it may be obvious that your laptop power supply has failed but this is often not the case. This article will help you decide if it is faulty or is failing.

You may notice any of the following symptoms that may be caused by a faulty or failing laptop power supply:-

1. If the power supply has an indicator light that does not illuminate when connected to the mains then the power supply (or the mains fuse) must be faulty. The power supply in this instance should not be connected to the laptop as some motherboard faults cause the power supply light to flash or extinguish.

2. If the power supply becomes very hot when in use then it may be faulty or be of the wrong rating for the laptop. It is easy to mix up similar units between laptops. Check that the rating on the laptop ie Volts and Amps match the charger rating. The charger should show the same voltage as the laptop, however, the current should be the same or higher from the charger. Sometimes when the charger becomes very hot then it may turn off and come back on again when it has cooled down. However, this is not a safe option and it should be replaced immediately.

3. Sometimes laptop chargers produce the wrong voltage either too high or too low. Generally this can be tested by a cheap multimeter, however, a true reading can only be made under full load when connected to the laptop. But as a guide, if the voltage is more than half a volt too high or too low then the charger may be faulty. If the voltage is too low then you may find that the battery does not charge fully or only charges when the laptop is turned off, however, a faulty battery or charging circuit may show the same symptoms. If the voltage is too high then the laptop will probably work correctly but it may get hotter than usual and or the battery may overheat and fail quicker than expected.

4. Everything may seem to operate correctly, laptop running and battery charging, then for no apparent reason the battery

may stop charging and or the laptop may turn off. This is often caused by the power plug that connects from the charger to the laptop failing. Sometimes the cable breaks where it joins the plug. This can occur if it has been sharply bent or is repeatedly been bent at this point. Generally wiggling the end of the cable will cause the battery to charge then not charge. Beware though this fault is often as a result of the internal laptop socket failing.

5. The laptop and charger may seem to be working ok but a high and potentially dangerous voltage may be present at the plug that connects to the laptop. Using a multimeter set to AC voltage measure between one connection (it does not matter which) of the plug that connects to the laptop (NOT the mains plug) and an earthed point, this could be any metal object connected to electrical earth. There should only be a very small or no voltage present. If a voltage is seen then the insulation inside the charger may be failing or has failed and may eventually let mains voltage enter the laptop! For safety you should immediately replace the laptop charger.

Laptop chargers are relatively cheap and should be immediately replaced if you suspect a fault is present as if ignored may cause an expensive laptop failure. If you use the manufacture's original unit the tip should exactly match the socket inside the laptop and generally they are smaller than the universal charges.


Graham has had many years experience repairing defective laptops, netbooks, notebooks and repair USB drives; specialising in fixing motherboards at component level for Laptop repair is always difficult but is very rewarding when an obscure fault is located and fixed.

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Have a question for Graham?

25th May 2014 12:19am
when i connect my charger to my pc it sometimes says plugged in but not charging i can use the AC but my batteries are not being charged but sometimes it works well. but new thing started yesterday it was working fine but suddenly my laptop shutsoff it wouldnt start for some minutes and i turned it on and it happened for second time?? what caused the problem is it my charger or my Laptop ??
4th June 2014 6:07am
sounds like a power supply unit issue or either a bad charger: battery may also be bad depending on your charging cycles that can diminish you battery life . more or less check the psu as well as the output of the charger.

Vincent Putelli
15th June 2014 8:23pm
I believe the issue is with the laptop, I have tried 4 different power supply pack on my laptop and every one of them the light indicator stops as soon as i plug it in the laptop. I then need to disconnect the power pack from the main and reconnected to the main for the light indicator to come back on the charger. If i used any of the 4 power pack supply with an other laptop they work fine. It seems that the faulty laptop does something to the power pack once plugged in. I cannot start up the ... Read More

30th June 2014 4:23pm
My laptop works fine with the plug in but the battery removed. If I insert the battery the laptop immediately shuts off. The battery is brand new. Any ideas? Thank you.

20th August 2014 9:45am
my laptop charger is 19.5V/4.62A/90W but when test it with a multimeter it shows 19.9-20 volt is it OK or faulty although my laptop is running normally.please clarify me the thing that is the problem with my multimeter or charger?

14th September 2014 1:58pm
My power turns on but not the screen. I take the battery out and unplug and leave for a week then it turns on again. I can use as long as I want but once it turns off it won't work
Again for a week or so....

Paul T
21st September 2014 8:16pm
Hi, I have a 4 year old 18'4 inch Acer 8390,g. It is now becoming very unstable and just switches off altogether sometimes 5 times In a row before starting up and being OK. My laptop battery is worn out and not holding charge for more than 5 mins and should be replaced.It works without any battery and AC power but is sometimes also unstable. The Power socket on the laptop used to get very hot and needed to be played with to work properly. That seems to trigger a switch off sometimes too. ... Read More

12th October 2014 9:32am
My laptop Acer aspire e1 510 only one month old.From one weak laptop off without warning at 40% battery remain always.When i tried to restart it cannot start. So i have to plug in again for charging after 5 min it start But it shows battery 5 or 6%.please help me.

26th October 2014 11:01am
Hey i wanted to ask something, is it possible for a Laptop charger to damage a battery, anytime I'm charging my comp, the system doesn't show that it's charging,but the charging light is on,and the percentage increases. i bought a new battery two days ago but after two days of behaving well, it doesn't charge at all, could the charger have damaged the battery?

6th January 2015 5:55pm
My laptop, (an Acer Aspire 5742 Series,) keeps shutting down without warning. It's usually after extended use. It could be a whole different problem, but it acts like it's overheating. For example, the fan starts to run as fast as it can, and even if I set the laptop on top of something so that it has good airflow, it still sometimes shuts off. This made me think maybe it has something to do with the power supply not being sufficiently cooled, but it happens constantly and gets really ... Read More

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