Dell OptiPlex 9020 (Mid 2013) - Manual (Page 22)

a) cover
b) front bezel
c) drive cage
3. Disconnect the fan cable and press the release lever down and outward to release the fan retention hook.
4. Flip the release lever and lift the top portion of the fan.
5. Loosen the captive screws and lift the heat sink assembly, and remove it from the computer.
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