An upper flipper sharing a button with a lower flipper has no power, or only works when the lower flipper completes its stroke.

Upper flipper weak or dead when the lower one is

Cause: The upper flipper's power stroke is enabled by the normally open second EOS switch on the lower flipper; if the lower flipper does not reach the end of travel or that EOS is dirty or misadjusted, the upper flipper gets no power.

Checks

• Check that the lower flipper flips fully.
• Inspect and gap the normally open EOS switch on the lower flipper.

Fix

• Fix the lower flipper, then clean and adjust its normally open EOS so it closes at end of stroke.

Systems

• Bally 6803

Games

• Eight Ball Champ

Related tips

• Upper right flipper completely dead: failing EOS switch
• Flippers dead and voltage reads nonsense: measure to the flipper board ground
• Upper flipper weak on a multi-flipper game

Source: Repairing Bally 6803 Pinball Games from 1985 to 1989, Clay Harrell (pinrepair.com)