The a/c on my 66 was not working, after allot of investigation and fooling around etc , I came across the switch etc, hard to get at , so I decided to remove the nut holding it in place , I brought it down low enough to have a good look at it, and noticed there is an adjustable screw on the vacuum shaft , after I loosened it and repositioned it the switch works fine , is there a reason for this adjustable piece ? trying to figure out why it there or what other purpose it serves, it appears only to trigger the a/c system after that the elect switch controlled by the sensing probe takes over ? any info would be greatly appreciated.