13.Remove the four rib frame screws. Three are identical black T8 screws, the forth is a longer chrome T8 and also secures the heat exchanger alignment bracket to the end of the heat exchanger. (You might need to move aside the AirPort antenna cable to reach one of the screws.)
Replacement Note: Make sure to replace the longer chrome screw through the alignment bracket so that it secures the small alignment nub on the end of the heat exchanger. Look from the side through the air vents of the top case to verify that the ribs on the heat exchanger do not block the vents.
14.Lift the rib frame off of the heat exchanger. If the heat exchanger sticks to the rib frame, press gently on the heat exchanger near the two connection points shown.
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