The control box in the VMAC hydraulic air compressor is the computer that tells the compressor what to do and when to do it. Control boxes also give a voice to air compressors and allow them to share important information via the display box that can help with system maintenance, operation, and diagnosing issues.
If your VMAC hydraulic air compressor doesn’t have a display box, it is an earlier model that utilized red and green indicator lights instead. These lights will display in patterns, similar to Morse code, to communicate. To learn more about these indicator lights and what their patterns mean, please visit the Hydraulic Air Compressor Error Codes guide in our Knowledge Base.
Top 5 Control Box Features
The VMAC hydraulic air compressor control box has numerous features, including:
5. Air Filter Reminders
The display box will remind you to check the air filter every 100 hours and it’s at your discretion whether the filter should then be replaced. The air filter reminder will go away on its own after 6 hours of operation.
4. Service Reminders
Every 500 hours, the display box will let you know that it’s time for servicing. Use the instructions in your VMAC service kit to complete this work, and then log the service work as complete. The hydraulic air compressor control box will maintain a record of the last ten system service times, for your record.
3. Temperature Warnings
The hydraulic air compressor also has a fail-safe mechanism that prevents the system from getting too hot by automatically shutting down. The display box will let you know whether it’s the air compressor or the hydraulic oil that is overheating, which will help diagnose and resolve the issue.
In addition, the display box will notify operators during start up if the hydraulic oil is too cold (below -13°F or -25°C) or in the process of warming up.
2. Errors & Service Diagnostics
The VMAC hydraulic air compressor will also display error messages on the display box. These error messages can help operators and service techs diagnose the issue and, as a result, implement the most efficient fix possible.
1. Modify System Parameters
One of the coolest features of the hydraulic air compressor control box is the ability to modify the system parameters from the default settings to the settings that make the most sense in your environment. You can modify the following parameters:
- System Pressure
- Temperature Sensor Overrides
- System Restart Pressure
- Standby Delay
You can also review the PSI and temperatures by pressing the ON button repeatedly until the data is displayed on the display box.
Change Your Hydraulic Air Compressor Defaults
| Setting |
Description |
Default |
Adjustment Options |
| Standby Delay |
Delay time to standby |
2 minutes |
30 sec, 45 sec, 1, 2, 5, 10, 15, 30 minutes, Never |
| System Pressure |
Maximum operating system pressure |
150 PSI |
110 to 150 PSI |
| Restart Pressure PSI |
Air pressure set-point for pressure-based restart |
120 PSI |
80 to 120 PSI (limited to 30psi or more below the UNLOAD PRESSURE) |
| Temperature Probe Override (Temporary) |
Override temperature controls to perform emergency system maintenance |
Disabled |
Enabled |
Hydraulic Air Compressor Display Box Messages
The following messages have been coded into the hydraulic control box and will be displayed on the display box:
Power ON, System Off
| Message/Problem |
Possible Causes |
Corrective Action |
| No power to display box |
Fuse blown or bad connection |
Check components, replace fuse inside system |
ON button pressed/initial start up
| Message/Problem |
Possible Causes |
Corrective Action |
| SOFT START XXXPSI |
The system has started, but the compressor oil temperature is still cool. |
The system is in “Unload” Mode, until the compressor has come up to temperature
+122°F (50°C). |
| HYD OIL TOO COLD |
The hydraulic oil is below -13°F
(-25°C). |
The system is cautioning the operator to preheat the hydraulic oil before starting the PTO system. The Cold Climate Kit (A700146) can be installed to speed up the warming process once the hydraulic oil temperature has reached –13°F (-25°C). |
| HYD OIL WARMING, HYD XXXF/XXXC |
The hydraulic oil is between -13°F(-25°C) and +5°F(-15°C). |
Keep circulating hydraulic fluid until the system warms sufficiently to start. If installed, the Cold Climate Kit (A700146) will speed warm-up. The System won’t start until the hydraulic oil has warmed to +5°F (- 15°C). |
| System does not start when the ON button is pressed. |
1. Inappropriate conditions for start-up.
2. Hydraulic solenoid failure.
3. Hydraulic motor or compressor seized. |
1. Check display box for messages.
2. Check solenoid and connections.
3. Check motor and compressor will roll-over. |
Running
| Message/Problem |
Possible Causes |
Corrective Action |
| STANDBY XXXPSI |
The air pressure stayed above the restart pressure for the duration of the standby delay time. |
The hydraulic solenoid is off, and the system is monitoring air pressure and compressor and hydraulic oil temperatures. If the air pressure drops below the restart pressure, or the
compressor oil temperature drops below its minimum, it will restart and rebuild air. |
Air pressure won’t build past approx. 40psi. |
1. The system is in SOFT START.
2. Unload solenoid on inlet valve has failed or problem with wiring connections.
3. Pressure sensor has failed or
problem with wiring
connections. |
1. Wait for the compressor to warm up.
2. Check solenoid and wiring.
3. Check pressure sensor and wiring. |
Low system air
pressure. |
1. Air reservoir drain open.
2. Air leak.
3. System demands
exceed compressor delivery.
4. Blowdown system stuck. |
1. Close valve.
2. Check all fittings. Check air lines for wear/damage.
3. Reduce air demand. Check for correct amount of hydraulic flow for the desired CFM.
4. Check for air venting from blowdown cap while running. |
| Compressor stalling/not building air. |
1. Hydraulic relief valve lifting.
2. Hydraulic flow too low.
3. Unload Solenoid Failure |
1. Check hydraulic pressure while running. Check for other relief valves in system set too low.
2. Check for correct amount of hydraulic flow for the desired CFM. Ensure that engine rpm is being maintained when load is applied.
3. Check solenoid and wiring. |
General
| Message/Problem |
Possible Causes |
Corrective Action |
OVER TEMP HYD -
Hydraulic oil is getting too hot and the compressor is shutting down. |
1. Insufficient air-flow or ventilation.
2. Fan not operating.
3. Failed temperature probe or bad wiring connections. |
1. Make sure the cooler is not blocked. Open door if installed in a cabinet. Improve ventilation.
2. Check connections. Check fan and relay.
3. Check the temperature probe and wiring connections in the hydraulic manifold. |
| HYD PROBE OPEN HYD PROBE SHORT |
Failed hydraulic temperature probe or bad
wiring connection. |
Check the temperature probe and wiring connections in the hydraulic manifold. |
| COMP PROBE OPEN COMP PROBE SHORT |
Failed compressor
temperature probe or bad wiring connection. |
Check the temperature probe and wiring connections. |
| PRESSURE SENSOR? |
Failed pressure sensor or bad wiring connection. |
Check the pressure sensor and wiring connections. |
| CONNECTION ERR |
Failed control box, display box, or bad wiring connection. |
Failed control box, display box, or bad wiring connection. |
BATTERY LOW or
System runs then shuts down, and display resets, but doesn’t restart |
1. Wires connecting to battery positive and ground too
small.
2. Low battery voltage. |
1. Check wire size requirements in the installation manual and install the correct
gauge wires.
2. Check wiring connections. Measure voltage at the input to the air compressor when it is running with the fan on to
ensure full voltage. Check charging system. |
| High oil consumption |
1. Compressor, hose, fitting, or cooler oil leak.
2. Compressor shaft seal leaking. |
1. Check system for leaks.
2. Pull off hydraulic motor and check for oil inside coupling. |
| Excessive oil in air line |
1. Excessive oil level.
2. Coalescer filter plugged.
3. Scavenge line plugged. |
1. Check oil level and adjust as needed.
2. Check and replace as needed.
3. Check scavenge line and fittings. |
| Water in air system |
1. FRL
(Filter/Regulator/Lubricator) failure.
2. Air reservoir not drained regularly.
3. Excessive water in compressor oil. |
1. Check drain on filter.
2. Drain reservoir.
3. Allow system to completely cool, and drain water from tank until oil comes out. Top up oil as per manual. |
| Air pressure relief valve opens. |
Compressor system pressure exceeding
200psi. |
Check pressure sensor. |
For further assistance with VMAC’s hydraulic air compressor, please call our technical support team at
1-888-241-2289 or visit the VMAC Knowledge Base.
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