I have an alienware 15inch R3 which I purchased last year December 12th (just within warranty), the AC is plugged in (180w) however it states "power mode (plugged in) - not charging" I have ran diagnostics on this via F12 and the following images show. The laptop which I received from Dell last year has not been altered in anyway - it is using the same battery and AC provided.
Have you tried a reset on the system yet? Disconnect the battery and unplug the adapter. Press and hold the power button for 30 seconds. Then reconnect everything and try again.
Make sure the BIOS is up to date.
Try a power drain and also, enter the BIOS and make sure the AC Adapter is being recognized.
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