Remove the valve  from the valve block with a crow foot wrench . Before you install the replacement valve, turn the main adjustment knob  on the adjustment valve counterclockwise until it stops.
Install the replacement adjustment valve with the crow foot wrench . Leave the screw on the locking jam nut  loose.
Refer to the link at the end of the document for the correct pressure. Do not exceed the correct pressure, or permanent damage to the chuck can occur. Slowly raise the pressure of the HPU to the correct maximum value: Turn the main adjustment knob  clockwise, check the pressure after each quarter turn. Repeat the process until the HPU is set to the correct pressure. The machine can generate a low pressure alarm until the correct pressure is set.
Turn the locking jam nut  clockwise by hand until it stops on the valve body. Rotate the valve and the locking jam nut  counterclockwise together until the screw on the locking jam nut  is accessible. Tighten the #4-40 thread screw on the locking jam nut  to 14 in-lb (1.6 Nm). Hold the locking jam nut  while you tighten the screw. Rotate the main adjustment knob  clockwise until the locking jam nut stops against the valve body. Make sure that the maximum pressure is correct. If the pressure is not correct, loosen the #4-40 thread screw and rotate the locking jam nut  to set the correct pressure.
Set the correct maximum pressure. Go to Chuck and Tailstock - Recommended Maximum Pressure on diy.haascnc.com.