Wire unit of the fan disconnected.

Check if the wire unit of the fan is connected with the Signal backplane See reference 2 image "Red DMD fan indication".

Check the fan connection with the wire unit to the signal backplane. See reference 1 image "Red DMD fan indication".

Blocked fan.

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

Damaged wire unit.

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

Fan end of life.

Replace the fan.

Malfunction Fan & Motor Control Board

Replace the Fan & Motor Control Board. See "Removing a board in the card cage".

Other fans are also not spinning.

Replace the SMPS Board. See "Replacement of the Switched Mode Power Supply".

Defect Signal Backplane

Replace the Signal Backplane, see "Replacement of the signal back plane".