MacBook power charging green LED not lit

My wife's 13.3" Macbook was exibiting an odd issue. The power connector has an LED on the MagSafe adapter right where it plugs into the side of the computer, and usually this LED is a solid bright green. However, she noticed that the LED, after a time, would become a very faint green. Usually if you jiggled it, it would turn bright again. This odd behavior didn't seem to affect the charging, and the system seemed to believe it was plugged in, even in the light was dim. My daughter has the same laptop, so we tried her MagSafe power adapter, and it did the same thing. So I used some 91% isopropyl alcohol and q-tip to clean up the connectors on the computer's adapter connector. After that, the LED has remained bright green, as it should.