Switches on the ninth column do nothing, and they never appear in the normal switch test.

Ninth switch column on Twilight Zone, Indiana Jones and STNG

Cause: These games add a ninth column through the 8-driver auxiliary board at the top far right of the backbox; the normal switch test does not show it. A bad or missing ribbon from the CPU board to that board kills the whole column.

Checks

• Use the game's own test for that column, such as the Clock Test on Twilight Zone or the right gun test on STNG.
• Check the ribbon cable to the auxiliary board.

Fix

• Reseat or replace the ribbon cable.

Systems

• WPC Fliptronics
• WPC DCS

Games

• Indiana Jones: The Pinball Adventure
• Star Trek: The Next Generation
• Twilight Zone

Related tips

• Indiana Jones ninth switch column
• Star Trek: The Next Generation ninth switch column (gun switches)
• STNG: under-playfield diverter coils lock on during play
• All flippers fire at power-up and blow the 50 V fuse: aux board ribbon upside down
• Solenoid numbers above 28 and the 8-driver auxiliary board
• One switch also triggers others in its column: bent diode on the mini playfield
• Spinner stops registering: broken wire on an upper flipper EOS switch
• Mini playfield switches misread and one switch shows as another: bad diode and miswire

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Two, Clay Harrell (pinrepair.com)