If the AC adapter is not working, does the battery not get charged when it is in the laptop? In other words, is there some other way the battery is being charged? Is it that the PC will not operate when the battery is out of the machine and the AC adapter only is present for power? If so, make sure that the power profile you are running under is set to allow the adapter to power the machine. To check this power setting (in XP), right-click on a blank section of your screen, choose Properties > ScreenSaver > Power. There could also be an issue within the Acer software utilities; particularly, it would be recommended to verify the settings in ePower Management.
If you still do not see any issues after these steps, please take the steps detailed here: http://www.acerpanam.com/synapse/forms/portal20.cfm?recordid=1125&formid=3390&website=AcerPanAm.com/us&siteid=7293&words=all&keywords=&areaid=7
This will help to ensure that there is no issue with the adapter itself; though, if the battery is charging using the adapter it appears that is not the problem.
Beyond this, I would say that the primary determinant lies in how the battery is being charged. If it is being charged with the usage of that adapter, then the problem would apparently lie with the connection of the adapter inside the notebook, for which a qualified technician will be required. If your machine is still under warranty, and it is determined there is some type of faulty connection, that should be covered.
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