Blocked Anode Fan (reference 2 image "Anode fan connections").

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

Damaged wire unit.

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

Malfunction Fan Control board.

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

Anode fan (reference 2 image "Anode fan connections") end of life.

Replace the Anode Fan. See "Lamp anode fan".