[Latitude 28]

I found this regulator in the R1 bay leaking air ever so slightly.  Tried to adjust to 120psi it only got worse.  I ordered a new Norgren P/N V07-100NNLA.  For lack of a better term this would be considered a pressure relief regulator as Richard stated above. Outside of the coach and on my bench I set up a normal regulator, with shop air, to approx 125psi output pressure and adjusted the new pressure relief set point to around 122psi.  Then I set the engine compressor governor to approximately 120psi.  Once installed and operational I only had to fine tune the relief set point.