The LED on a MacBook (13-inch Late 2009) MagSafe power adapter does not illuminate at all when it is plugged into the MacBook and you know the adapter is connected to a known good power source. What is the most likely cause of this symptom?
The MacBook has a faulty backup battery.
The MagSafe adapter needs to be reset first.
The MacBook has a faulty magnetic sleep sensor.
A MagSafe adapter connector pin is stuck down or dirty.
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