The upper right flipper (the Bally-style one) does nothing, although the button switch, wiring, coil and driver transistors check good.

Upper right flipper completely dead: failing EOS switch

Cause: The EOS switch on that flipper was failing. On these flippers it is normally closed and is part of the circuit, so a bad one can stop the flipper entirely.

Checks

• Check the EOS contacts are closed at rest and make good contact.

Fix

• Clean, adjust or replace the EOS switch.

Systems

• Bally 6803

Games

• Truck Stop

Related tips

• Double EOS switches drive the upper flipper
• Upper flipper weak or dead when the lower one is
• Standard 6803 flipper coil
• Games without the keypad use the flipper and start buttons
• One flipper sometimes locks on: cabinet switch contacts pitted and sticking

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