The flipper sticks in the up position and does not fall when the game is switched off.

Flipper stuck up and stays up with the power off

Cause: The worn rubber coating on the flipper pawl hangs on the end of the EOS switch (which may be frayed), a mushroomed coil stop lengthening the stroke, the flipper too tight in its playfield bushing, or a broken or missing return spring.

Checks

• Inspect the pawl and EOS switch blade.
• Check the coil stop.
• Check for vertical play in the flipper (about 1/32").
• Check the return spring.

Fix

• Rebuild the flipper, replace the coil stop, reset the bushing gap with the flipper adjustment tool, or replace the spring.

Systems

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

Related tips

• Flipper energises at power-on (Fliptronic)
• Flipper stuck up: turn the game off to tell mechanical from electrical
• Pre-Fliptronics: flipper runs very hot or sticks up and burns
• Both flippers lock on at power-up after a teardown: reseat the flipper connector
• Right flippers energized at power-up: replace the ribbon cables
• Flipper fires then falls straight back
• Flipper works on and off or drops while held
• Pre-Fliptronics WPC flipper stuck up with power on: failed driver TIP102

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