Q:

AC not working properly

Yesterday evening i used my laptop without any issue, this morning i went to work and i have noticed that the AC charger is not working properly. This is the behavior:  

If i connect the laptop to the charger while the laptop is not on I see the "power" LED up, if there's the battery the LED is blinking from red to white  (i think it means the battery is charging) 
If I try to power up the laptop i see the "power" LED up but the laptop uses the battery as power source rather than the AC, if i unplug the AC then plug it back in, it charges for few seconds then stops. I have to unplug the AC from the laptop in order to make it recognize the charger has been unplugged, if i unplug the charger from the power socket it won't recognize that the charger has been unplugged
If i try to power the laptop with the battery unplugged but the charger on, it will power up for 1 second and then in shuts down again

Now i want to know what it's not actually working (the charger probably, but i'm not sure), what tests can i run to rule things out?
The PC is an HP dv6 3011el and it's not under warranty anymore

A:

The most likely cause is the charger.  It's also the simplest to replace. The easiest way to test would be to try another HP charger if you can get hold of one. It may not need to be the exact same laptop model - it's likely that the charger output ratings do not necessarily change for different laptops from the same manufacturer.
My HP charger output (for what it's worth) is 19.5V 3.33 A 65W.

