What to do when the xbox 360 ac power adapter has a red light?

Simply unplug your "brick" from your 360 and your wall, if it is hot move it to a well ventilated area and allow it to cool for several hours, when it have cooled down try plugging it back up and everything should work fine, if not you may need to contact Microsoft.

For other light indicator meanings and solutions on how to fix it, i will recommend you to read the tutorial article at: http://www.unique-stuff.co.cc/fix_xbox_ac_adapter_problem.html

It has lots of solutions on how to fix different light indicator on both your console and XBOX ac adapter.