Lamp House is not correctly installed.

Check if the Lamp House is properly installed. Make sure that both fixation screws (reference 1 image) at the base of the Lamp House are fastened. See service manual chapter "Installation of the Lamp House"

Defect micro switch (reference 2 image).

Replace the micro switch.

Wire unit of the micro switch (reference 3 image) disconnected from the Signal Backplane.

Check if the wire unit (reference 3 image) is plugged in on the Signal Backplane.

Wire unit of the micro switch (reference 2 image) disconnected from the micro switch.

Remove the Lamp House, loosen the two screws of the micro switch and pull out the micro switch. The black wire unit of the micro switch must be connected with the red wire unit (reference 2 image).