As soon as the game is switched on the score motor keeps running and never stops, so the game cannot be played.

Score motor won't stop turning at power-on: wire broken off a score reel switch stack

Cause: A wire had broken off a switch stack on one of the score reels (probably disturbed during cleaning and adjusting), leaving a circuit that keeps the motor running.

Checks

• Look over every score reel switch stack in the head for a wire broken off a solder lug, especially after recent cleaning.
• Use the schematic to follow the score motor relay circuits even where relay labels are missing.
• After any repair, make sure nothing (such as a slip of paper used while testing) is left between switch contacts.

Fix

• Resolder the broken wire to its lug on the score reel switch stack.

EM games run some circuits at line voltage; unplug the game before working in the head.

Systems

• Electro-mechanical

Games

• Lucky Ace

Related tips

• Check the score motor switches before power-up
• EM score motor will not stop
• Players 3 and 4 reset but players 1 and 2 never do at game start
• Reset stalls with the player unit stuck at step 20: broken wire to a score reel
• Score motor keeps running at game over, O relay stays in: score motor 2C switch
• Score motor keeps running after start is pressed
• How the score motor resets the reels
• Score motor runs on and the game never starts

Source: Pinball Repair help group!! (Facebook group)