Service Home How To Procedures Hydraulic Counterbalance - Pressure Switch - Replacement - VMC - AD0331
Last updated: 10/24/2025

Hydraulic Counterbalance - Pressure Switch - Replacement - VMC

AD0331

Applies to machines built from: May, 1995 to May, 2012

Introduction

This procedure tells you how to do these tasks:

  • Release the nitrogen gas from the tank.
  • Replace the pressure switch on the tank for a hydraulic counterbalance.
  • Fill the tank with nitrogen gas to the correct pressure.
Tools Required
  • Charge/Discharge Kit, (part number 35-4050A)
  • Regulated dry nitrogen tank, 250 cu ft (7079 liters). The gas supply must have a right-hand thread, CGA 580 (.965-14 NGO-RH-INT) fitting. Welding grade gas is acceptable.
Document Applies to these Parts
  • 32-0022B    SWITCH, PRESSURE 900 PSI
  • 32-1006B    SWITCH, PRESSURE 750 PSI
  • 32-3004B    SWITCH, PRESSURE 600 PSI
  • 32-3006B    SWITCH, PRESSURE 1000 PSI
  • 32-3008B    SWITCH, PRESSURE 450 PSI
  • 32-3009B    SWITCH, PRESSURE 1400 PSI
  • 53-0015       SWITCH, PRESSURE 1000 PSI (SOLID STATE)

Mechanical Safety

 Caution: When you do maintenance or repair on CNC machines and their components, you must always follow basic safety precautions. This decreases the risk of injury and mechanical damage.

  • Set the main circuit breaker to the [OFF] position.
  • Use an approved lock with an approved safety tag. Always follow lock-out procedures in accordance to local government rules.
  • After turning off the machine, wait at least 5 minutes before working in the control cabinet, to allow power to dissipate. Wait for the voltage indicator LED on the vector drive to go off completely.
  • Always turn off the main air supply when you work on any part of the pneumatic system.
  • Make sure to rest the spindle head on a block of wood when work is done on a vertical axis. This will prevent any unintended movement that could result in the axis falling.
  • Never alter any safety circuits on the machine.
  • Never change any parameter while in DEBUG mode (Classic Haas Control) and the servos ON. Put the machine in Emergency Stop mode to change any parameters.
  • Never operate the machine in DEBUG mode (Classic Haas Control).

You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes. Serious damage to the machine components can result in costly repairs. The service technicians at your Haas Factory Outlet (HFO) have the training and experience, and are certified to do these tasks safely and correctly. The repair and service work performed by your HFO is protected with a limited warranty.

 Danger:  Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not fully understand. If you have any doubts about doing a procedure contact your Haas Factory Outlet (HFO) and schedule a service visit.

VMC - Hydraulic Counterbalance - Pressure Switch - Replacement

1

Jog the spindle head to 14.5" (36.8 cm) above the table.

Put a wood block on the table. Lower the spindle-head casting onto it.

 Caution: Do not let the spindle touch the block. This causes damage to the spindle.

Push [POWER OFF].

Set the main circuit breaker to the OFF position. Lock the main circuit breaker. Use an approved lock with an approved safety tag.

2

Disconnect the two-pin end of the pressure switch cable [1] from the pressure switch.

 Danger: Do not disconnect the hose [2] to the hydraulic cylinder.

Remove the tank from the machine. Do not twist the hose [2] for the hydraulic cylinder. Put the tank vertically on the ground.

Remove the cap [3] from the Schrader filler valve.

 Note: If your system has a two-end tank system, a second Schrader valve is at the bottom of the tank. Remove the cap from the top valve.

Turn the T-handle fully counterlockwise on the gas chuck [4] attached to the "Charge/Discharge-Kit" (part number 35-4050A).

With your fingers, tighten the nut on the gas chuck onto the Schrader valve.

Put the other end of the hose into a bucket.

Slowly turn the T-handle clockwise until the system starts to release the nitrogen gas. The time for this to complete is 10 minutes or less. Make sure the pressure gauge shows 0 psi.

Turn the T-handle fully counterclockwise and remove the gas chuck [4] from the Schrader valve.

3

Remove the used pressure switch.

Install the PRESSURE SWITCH ASSY 1400PS [A]. Use a wrench to tighten the switch.

With your fingers, tighten the nut on the gas chuck [1] attached to the Schrader valve.

 Note: Make sure you turn the T-handle of the gas chuck fully counterclockwise.

 Note: If your system has a double-ended tank system, a second Schrader valve is at the bottom of the tank. Use the top valve.

Attach the other end of the hose to the source pressure [2]. Slowly open the valve on the source pressure while you monitor the pressure gauge. Open the valve slowly at the start to protect the seals in the Schrader valve.

4

Pressurize the system to the correct psi (bar). For the correct value, refer to the chart at the end of this procedure.

Install the tank into the machine.

Push [ZERO RETURN]. Push [Z].

Examine the tank and hoses for leaks or unusual noises. Make sure the tank pressure is correct at the top of travel. Add nitrogen if necessary. Remove the "Charge/Discharge-Kit". Replace the valve cap.

Counterbalance Pressure Chart

This chart shows the correct pressures for the counterbalance tank. Measure the pressure at the top of Z-Axis travel for VMCs and at the top of Y-Axis travel for HMCs. Pressure that is 50 psi (3 bar) higher than the value in the chart is permitted. But pressure that is lower than the value in the chart is not permitted.

Model Made After Pressure Made After Pressure Made After Pressure
    PSI BAR   PSI BAR   PSI BAR
EC-1600/2000/3000 3/15/2004 1000 70 9/13/2004 550 38 6/14/2005 800 55
EC-630 3/21/2006 800 55            
HS-1 10/30/1997 600 51            
HS-3/4/7 6/5/1998 1150 79 6/18/1999 1200 83 2/29/2000 1250 86
VB-1 6/5/1998 1550 107            
VF-3/4 (VCE 1000/1250) 4/28/1995 1150 79            
VF-5 XRT 10/8/2004 750 52            
VF-5, VM-3, VF-3YT (VCE 1300) 7/21/1998 950 66 10/14/1998 875 60      
VF-5/50, VF-3YT/50 (VCE 1300) 7/21/1998 1100 76            
VF-6/7/10/12 - 50 (VCE 1600, 2000, 3000) 10/30/1997 1150 79            
VF-6/7/10/12 (VCE 1600, 2000, 3000) 10/30/1997 750 52            
VF-8/9/11 - 50 (VCE 1600, 2000, 3000) 7/21/1998 1550 107            
VF-8/9/11 (VCE 1600W, 2000W, 3000W) 10/30/1997 750 52            
VF-O/OE/EXT/1/2 (VCE 475/500/550/700/750) 4/28/1995 750 52            
VR-8/9/11 10/30/1997 1800 124 7/21/1998 1100 76 10/14/1998 1025 71
VS-1/2/3 2/29/2000 1250 86            
VTC 5/4/2002 1150 79