The charger (AC MagSafe adapter) appears not to be working correctly. On the left of this Wiki is the pin out for it. The pins may be stuck and not extending correctly or the unit may have failed. Unplug it and use something like a tooth pick to move the pins in and out. If this is working, use a multimeter to test the output. See if you are getting 16.5 volts from pins 2 & 4 : http://en.wikipedia.org/wiki/MagSafe