After a flipper rebuild the upper right flipper is very weak, often does not travel far enough to reach its own EOS switch, and will not hold up, while the lower flippers work well. Voltage at the coil looks the same as on the good flippers.

Upper right flipper weak and won't hold: dirty EOS switch on the lower right flipper

Cause: A dirty end-of-stroke switch on the lower right flipper, which shares the circuit with the upper flipper, was cutting the power to the upper coil.

Checks

• Check whether the upper flipper gets weaker the higher it is held by hand, and whether it can hold at all.
• Compare the lower flipper on the same side: a slow lower flipper, or one that bounces when a ball hits it while held, points to its EOS switch.

Fix

• Clean (or replace) the EOS switch contacts on the lower flipper and set the gap so it opens only at the very end of the stroke.
• Clean and gap the upper flipper's EOS switch the same way.

Systems

• Bally 6803

Games

• Motordome

Related tips

• Upper right flipper completely dead: failing EOS switch
• Double EOS switches drive the upper flipper
• Upper flipper weak or dead when the lower one is
• Standard 6803 flipper coil
• One flipper sometimes locks on: cabinet switch contacts pitted and sticking

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