I changed the icon to the machine you said you have.
Let’s get some information first:
Here is the pin out for the Mag-Safe:
Pin 1GND (0 V)
Pin 2V+ (14.5 / 16.5 / 18.5 / 20 V DC)
Pin 3Charge control pin
Pin 4V+ (14.5 / 16.5 / 18.5 / 20 V DC)
Pin 5GND (0 V)
What is the wattage of your Mag-Safe? What are your readouts?
When you plug it in what color is it and does it change within 10 seconds?
Try an SMC reset:
Connect the power adapter to the Mac. On the MacBook / Pro's keyboard, hold down the Shift+Control+Option keys and the Power button at the same time. Release all keys and the power button at the same time – the little light on the MagSafe adapter may change colors briefly to indicate the '''SMC''' has '''reset'''.