Blocked fan.

Remove the large dust filter from the projector and check if the small fan can turn freely (reference 1 of image).

Damaged wire.

Remove the large dust filter from the projector and check if the wire of the Card Cage small fan is damaged. Repair if possible, otherwise replace with new one.

Note: Electronics fan 1 (Card Cage small fan) is the fan which wire is marked with a yellow cable tie (reference 3 of image). Electronics fan 2 (Card Cage large fan) is the fan which wire is marked with a orange cable tie (reference 4 of image).

Fan end of life.

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

Malfunction Cinema Controller.

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