My MacBook was actually having trouble to charge the battery and the LED on the plug of the MagSafe was switching on/off without any good reason. I made a "cross test" : I pluged my MagSafe Power Adaptor to another laptop and the LED was staying on. So the Adaptor was not the one to blame :).
Then I pluged a recent Power Adaptor to my MacBook and the LED problem appeared again.
So I decided to change the plug of the computer which is attached to the DC-In Board card.
The repair was quite difficult : all the screws in the MacBook are tightened with some "threadlock" which makes them hard to remove. I was unable to remove them using the screwdriver that I bought from the iFixit website. I instead had to use a high-quality (Facom) screwdriver.
The guide was easy to follow, but the first time I didn't put back the keyboard ribbon cable correctly and the computer didn't start :(. In fact, the power button is connected to the keyboard, so you really need to make this one fit correctly in its place.
- Buy a top-quality screwdriver, otherwise you may have trouble trying to remove the MacBook screws.
- Don't forget to fully push the keyboard ribbon cable (step 15 in the guide) back into its place after changing the part, otherwise the computer will not start ;)