Blocked fan (reference 4 of image).

Unblock the fan. Ensure that the fan can turn freely.

Damaged wire unit (reference 3 of image) of the bottom card cage fan (reference 4 of image).

Remove the front cover and front dust filter from the projector and check if the wire unit of the fan is not damaged. Repair if possible, otherwise replace with new one.

Remove the front cover and front dust filter from the projector and check if the wire unit (reference 5 image) is not damaged.

Note: Card cage fan 1 is the fan which wire unit is marked with a yellow cable tie. Card cage fan 2 is the fan which wire unit is marked with a orange cable tie.

Malfunction Fan Control board.

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

Fan end of life.

Replace the fan. See service manual chapter "Replacement of the Card Cage fans".