The display reports a short on a switch row (named by its white wire color).

"Row Short" message

Cause: That switch row is touching ground somewhere.

Checks

• Check coin door switches are not touching the grounded coin door.
• Check playfield leaf switches are not touching grounded metal.

Fix

• Move or insulate the switch blade or wire that touches ground.

Systems

• WPC Alpha-Numeric
• WPC Dot Matrix
• WPC Fliptronics
• WPC DCS
• WPC-Security (WPC-S)
• WPC-95

Related tips

• "Ground Short Row" message
• "Check Switch ##" message
• Switch matrix wire colors (all WPC games)
• "Check Switch #" message at start-up
• Row or column "ground short" errors
• A row wire on the wrong end of a switch diode creates ghost switches
• Most of switch row 6 dead, last switch works: broken row wire
• Several switches in one row or column dead: a broken daisy-chain wire

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