Blocked fan.

Unblock the fan. Ensure that the fan can turn freely (reference 3image).

Damaged wire.

Check if the wire of the fan is not damaged. Repair if possible, otherwise replace with new one (reference 4 image).

Fan end of life.

Replace the fan. See service manual chapter "Replacement of the Cold Mirror fan".

Malfunction Cinema Controller.

Replace the Cinema Control board. See service manual chapter "Replacement of the Cinema Controller".