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How to replace all wifi antenna cords?

The antenna unit is held within the black clutch cover between the display hinges. You’ll need to take the display off to gain access following this guide MacBook Pro 13" Unibody Mid 2012 Display Replacement. Once the display is removed you can then slide the clutch cover off sliding it toward the hinge to unlatch it. Once off you can then replace the assembly Unibody MacBook Pro 13" Antenna, Apple P/N 818-1821