Compressor not cutting out

What model dryer do you have? Check the line from the governor to the compressor. Also check the line from the governor and trace it to the air tank. The governor senses/reads the air pressure from the tank. When it reaches the set pressure of about 120-130 psi the governor then opens to the control line that goes from the governor to the compressor. The air pressure opens the unloader valve and air is not sent through the discharge line to the tanks.

 

Have you checked the supply line to the governor? I would make certain that it's not blocked.

Assuming your purge valve isn't popping off at normal pressure?

 

Have the gauges been checked for accuracy? Is the gov adjustable and was it dialed in? The proper plugs removed/ installed in the proper ports on replacement gov? Most systems should have a safety pop off valve on a tank somewhere that should release pressure around 150 psi. to keep a runaway compressor or bad gov from building dangerous levels.
I’ve seen many air gauges be liars in many trucks. Had one recently that would build air to 125 and purge like supposed to but gauge would not rise past 90. Funny thing was it was balls on accurate to that point with the low air buzzer and knobs pop out point.