The control switch lives on top of the steering column down near the firewall. You'll find the vacuum hose coming in through the firewall attached to it, and the other hose going away from it to the vacuum release mechanism.Secondly I think this has been talk about in the past but I can't find it now, any Ideas were to find the E brake vacuum switch for my 75. I have for the time just blocked off the line to it, this stopped the snake under there from hissing.