One flipper buzzes (flutters) when held up and feels weak; adjusting the switch can make it sluggish or stick.

Flipper flutters and is weak: end-of-stroke switch and binding bracket

Cause: On this game it was both a bad end-of-stroke switch and a bracket that let the plunger bind on its way into the coil. A hold winding broken at the coil lug causes the same flutter.

Checks

• Watch the end-of-stroke switch: it should open cleanly when the flipper reaches the top and stay closed at rest.
• With power off, work the flipper by hand: it should move freely with no drag. Check the coil bracket and base are tight and square, and the coil sleeve and link are not worn.
• Look for a spark at the coil lugs while the flipper is held; that points to a broken hold winding.

Fix

• Replace or regap the end-of-stroke switch.
• Realign and tighten the coil bracket so the plunger runs straight into the coil; replace a worn sleeve or link.
• Resolder or replace the coil if the hold winding is broken.

Systems

• Williams System 4

Games

• Flash

Related tips

• Flipper flutters when held up
• Weak, chattering or buzzing flipper: end-of-stroke switch
• Flippers dead, flipper relay only buzzes faintly: replace the relay's diode D1
• Most flipper faults are EOS switch faults
• Weak flippers
• Flipper sticks in the up position
• Games with an upper flipper switch on the EOS stack
• Flipper coil gets very hot

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