We recently refurbished the turn and bank indicator regulator bellows for our Blue Boxes. The regulated vacuum output is supplied to a gyro inside the turn section of the turn and bank indicator.
For more details, read the ‘turn and bank indicator regulator bellows’ section under ‘Restoration hints’ in the right column [scroll to bottom for cell phone] , or check out our video.
Update December 1, 2020. The bellows refurbishing did the trick. The turn and bank indicator is now working. Yea!