HP 9020 Service Manual page 169

Assembly Access
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9. From rear of computer, remove four #2 Pozidriv screws that attach 110 card cage fan to
computer (Figure 4-73) and remove fan.
10.
Remove four clips at corners of fan and retain for installation on replacement fan.
#2 POZIDRIV SCREW
Figure 4-73. Removing I/O Card Cage Fan
Reassembly Notes
Attach four clips to corners of fan before attempting to install fan in
computer.
Install replacement fan in computer with airflow direction arrow pointing
toward rear of computer and plug receptacle at upper right corner of fan
(as viewed from rear of computer).
Ensure proper polarity of fan and fan cable.
Ensure fan cable is not pinched when computer is reassembled.
Ensure ribbon cables are inserted in clips mounted on underside of ac
module.