Dell Precision 7920 Tower Owner's Manual page 21

4. To remove the fan, release the fan connector cable from the latches [1] and [2].
5. Remove the screws that secures the fan to the air shroud [1], and lift the fan away from the air shroud [2].
NOTE: The shroud will need to be flexed open slightly in order to be removed.
Removing and installing components 21