If flipper coils are not wired correctly (on most games 1991 onwards until mid 1994, a bulletin for later machines will be added shortly) serious damage will be caused to the flipper control board.
The following diagram illustrates how to connect the flipper coil correctly.
All Bally/Williams game manuals have the correct flipper coils listed inside the front page. It is important to install manufacturers recommended part to avoid damage to game and maintain optimal performance.
A brief guide of which coil should be installed is as follows...
Close ramp shots, very close to targets, generally upper flippers. (Coil Ref No. FL-11630 Red paper).
Medium ramp shots, upper loops, near targets. (Coil Ref No. FL-15411 Orange paper).
Steep ramp shots and long range shots. (Coil Ref No. FL-11629 Blue paper)
The common reason for poor flipper performance is wear in the mechanical parts. If you are workshopping your own game that was bought elsewhere you will probably be best off replacing all the moving parts. Namely; plunger & link (P/N A-15847), end stop (A-12390), plastic bushing (03-7568), spring (10-364), flipper coil, on pre 1992 games, change the end of stroke switch (03-7811). Sometimes the flipper crank assy needs changing, so just change the whole plunger, link and crank assy (A-15848- left or right).