Early pressure regulators in ID/DS were a very simple ball and spring arrangement much like the pressure regulator in a power steering system, but all the pressure regulators from the GS in 1970 up until the Xantia are a dual shuttle valve system that operates as a positive feedback bistable with hysteresis, (much like a 2 transistor bistable for those of you with an electronics bent!) hence the different cut in and cut out pressures and the very positive snapping open and shut action rather than the constant partial leakage you get with a simple ball and spring relief valve system.taffy wrote:So what regulates The pressure at The accumulater block...spring and ball bearing or electro valves?
For whatever reason it's the cut-out click that is loud and audible as the pressure reaches maximum. I usually can't hear the cut-in click over engine clatter unless the regulator is badly worn...
Here is the internal diagram: (click for full image)