On some machines, you cannot adjust the regulator.
Use the pressure-gauge assembly to make sure the regulator operates correctly:
Push and hold the button on the pre-charge solenoid valve  for 20 seconds.
Pull the regulator adjustment knob to unlock it.
Set the air pressure to:
- Belt/Gearbox: 4 psi (0.28 bar)
- Inline: 30 psi (2.1 bar).
Release the solenoid button.
Push and hold the button on the solenoid valve , again for 20 seconds.
Make sure the gauge is reading the values you set above. Release the solenoid button. Push the regulator adjustment knob to lock it.
If the regulator is not adjustable, check to see if it measures the same pressure values as above.
If the gauge does not shows the correct pressure, the regulator is defective. Replace the regulator.
Remove the service kit assembly from the regulator.