Wire unit (reference 1 image) of the Cathode Fan is disconnected.

Remove the left side cover of the projector and check the connection of the Cathode Fan.

Wire unit (reference 5 image) of the fan units is disconnected from the Signal Backplane.

Remove the front cover and front dust filter from the projector and check if the wire unit (reference 5image) is inserted in the Signal Backplane.

Blocked Cathode Fan (reference 2 image).

Check if the Cathode Fan is not blocked. Ensure that the Cathode Fan can turn freely.

Damaged wire unit.

Check if the wire unit of the Cathode Fan is not damaged. Repair if possible, otherwise replace with new one.

Malfunction Fan Control board.

Replace the Fan Control board. See service manual chapter "Replacement of a Card Cage board".

Cathode fan (reference 1 image) end of life.

Replace the Cathode Fan. See service manual chapter "Replacement of the Cathode fan".