The Light Processor Unit is not correctly installed.

Check if the Light Processor Unit is properly installed. Ensurethat both fixation screws at the foot of the Light Processor Unitare fastened. Check if the Formatting Interface Board is well insertedand secured.

Switch disconnected.

Check connection of engine switch at the Power Backplane, ifconnections are OK, measure switch at connector for continuity.

Damaged switch.

Remove the Light Processor Unit and check that switch is notdamaged. The switch is located behind left hand side set pin whichguides the engine into place. Replace switch if needed.

Malfunction Fan Control Board.

Replace the Fan Control Board.

Defect Power Backplane.

Replace the Power Backplane.