Use a 2.5mm Allen wrench to loosen the four screws securing the front cover to the middle plate, and the three screws securing the front cover to the bottom plate.
Use a 2.0mm Allen wrench to loosen the two screws on the left side of the front cover, and the two screws on the right side. Lay the front cover flat on the table.
Use a 2.0mm Allen wrench to loosen the five screws securing the left side cover. Remove the left side cover.
Use a 2.0mm Allen wrench to loosen the two screws on the right side of the back cover, followed by the two screws on the left side, and the three screws underneath.
Use a 3.0mm Allen wrench to loosen the three screws on the top of the back cover. Next, switch to a 2.5mm Allen wrench to loosen the remaining two screws on the top.
After removing the screws securing the back cover, lay the cover flat and disconnect the UV light connector.
Disconnect the cables from the FAN1 and FAN4 ports on the motherboard (red-black cables).
Undo the twist clip securing the cable bundle and pull out the two cooling fan cables.
Use diagonal pliers to cut the zip ties securing the fan cables. Use a 3.0mm Allen wrench to loosen the four screws securing the two cooling fans on both sides.
Take out the two new cooling fans. Insert the two screws into the mounting holes of the fan with the long cable, align the fan with the left-side mounting position, and tighten the screws with a 3.0mm Allen wrench. (Note: Align the side with the label to the outside.)
Insert the two screws into the mounting holes of the fan with the short cable, align the fan with the right-side mounting position, and tighten the screws with a 3.0mm Allen wrench.
Securely fasten the two fan cables in the twist clip. Reconnect the connectors to their respective ports on the motherboard.
Place the back cover back in its position and reconnect the UV light connector.
Align the back cover with the screw holes and install it back in place. Use a 3.0mm Allen wrench to tighten the three screws on the top of the back cover. Next, switch to a 2.5mm Allen wrench to tighten the remaining two screws on the top.
Use a 2.0mm Allen wrench to tighten the two screws on the right side of the back cover, followed by the two screws on the left side, and the three screws underneath.
Align the left side cover with the screw holes and install it back in place. Use a 2.0mm Allen wrench to tighten the five screws securing the left side cover.
Align the front cover with the screw holes and install it back in place. Use a 2.0mm Allen wrench to tighten the two screws on the left side of the front cover, and the two screws on the right side.
Use a 2.5mm Allen wrench to tighten the four screws securing the front cover to the middle plate, and the three screws securing the front cover to the bottom plate. The cooling fan replacement is now complete.