I am trying to set the turning movement of the needle in zig zag on a Viking Emerald 116/118

SOURCE: Kenmore 1560 Sewing Machine

Be sure TOP control shows zig-zag. Flip top right bar from red to black or black to red on side of machine facing you. You can then change the widths by changing the numbers on that same circle control.

SOURCE: the zag part of zig zag won't work

i believe your machine is skipping the stitch on the RIGHT side as you sew and this is normally a timing problem. Lower your needle about 1/16 inch and try it . It might work to finish your project but it will need to be serviced to have the timing corrected.
sewman7

SOURCE: ZIG-ZAG NOT WORKING

Make sure your presser foot is tight down. If the needle is going from side to side, it's doing it's job. If the stitches are coming out straight, the material is probably slipping back and forth to center area. The presser will eliminate this.

SOURCE: Needle stop up/down no longer works on Viking 118

sometimes the bobbin winder gets left closed, and that will make the machine run slowly and with no up/down button.

SOURCE: Pfaff 362 won't zig zag

yes, it's very possible that the control/knob needs to be replaced
or the cam or gear that works the zigzag