Apple Xserve Intel (Late 2006) DIY Procedure for Logic Board - Manual (Page 8)

Xserve (Late 2006) Logic Board Replacement Instructions 
Note: You may encounter some resistance around the fan array power connector during removal.
If so, carefully rotate the fan array as shown to disconnect it from the power distribution board
below, and then lift the fan array out of the computer.
Backplane-to-Logic Board I/O Cable
Disconnect the backplane-to-logic board cable from the logic board. 1.