663. The winch shown in the illustration operates in any of the positions with the master switch in the 'lower' direction, but will not 'hoist' in any of the master switch hoist speed positions. Which of the listed faults could be the cause

The hoist fails in all speeds while the lower function operates normally, indicating a fault specific to the hoist circuit and common to all hoist speeds. Master switch contact MS 4 is closed in all hoist positions and no lower positions; a defective spring on MS 4 would prevent the hoist contactor from energizing, thus disabling hoisting while leaving the lower function unaffected.