I just finished rewriting my air brake endorsement last month and aced it. 55psi is the minimum for the buzzer to cut in and must cut out no later or higher than 60psi. Normal operating pressure is between 80 psi and 135 psi. fooling around at 65 is only fooling and confusing yourself. Air it up to where the governor cuts out and then try releasing and if that doesn't work then forward and back. I'm confident it didn't cease up too severely in a month. Good luck