You may be right but it's not from the TYPE of device or how it works. This is caused by things like corrosion, rust, and other malfeasance plugging up the switch / piston mechanism. This is a piston operated switch. It is not a valve.
A good read...........
http://www.mymopar.com/downloads/mtsc/232.pdf
n a movie
MTSC - 1967, Volume 67-3 Dual Hydraulic Brake System - YouTube
