Why does the screw air compressor display “load” but fail to draw in air after startup?

I. Malfunction of the intake valve and the control solenoid valve

The intake valve is the core component that controls air intake in an air compressor. When the control panel sends a loading signal but the intake valve fails to open properly, the system may display “loaded” while no air is being drawn in. Common causes include:Intake valve mechanically seized, the valve disc is damaged, or the component that controls the operation of the intake valve…Solenoid coil burnoutThe valve spool is stuck, preventing the control air from actuating the inlet valve to open.

II. Control for Air-Leakage or Blockages in the Pneumatic Circuit

The air intake valve of an air compressor is typically actuated by an internal control air circuit. If the control air circuit malfunctions, the intake valve will fail to receive the opening command.

• Tracheal rupture or dislodgement: Control of tracheal aging and rupture, or loosening of joints, can lead to leakage of control air pressure, preventing sufficient pressure from being built up to open the intake valve.
• Orifice blockage: The small throttling orifice in the control line becomes clogged with oil contaminants or debris, preventing airflow and keeping the intake valve closed.

III. The minimum pressure valve is seized.

The minimum pressure valve is located at the outlet of the oil‑gas separator tank. Its primary function is to maintain system pressure and prevent backflow of gas. If the valve spool becomes stuck in the closed position due to contaminants, or if the return spring breaks, even though the compressor unit is normally compressing air, the gas will be unable to vent outside the machine. In such cases, the external symptoms closely resemble those of no air intake or no air delivery.

IV. Errors in Sensors and Control Systems

The control panel displays the load status based on the feedback signal from the pressure sensor. If…Pressure sensor failureAlternatively, poor contact in the signal transmission lines may cause the controller to receive incorrect pressure data, leading to erroneous logical decisions. Furthermore, incorrect parameter settings within the controller can also result in the system displaying a load condition while, in reality, no actual load‑control signal is being output.

5. The air intake filter element is severely clogged.

The air intake filter’s function is to trap impurities from the incoming air. If it is left unchanged for an extended period, the filter will become severely clogged with dust and oil, causing a sharp increase in intake resistance. In such cases, even though the intake valve remains open, the excessive physical resistance results in only a negligible amount of air entering the compressor, manifesting as extremely low discharge flow or virtually no air output.

VI. Recommendations for Routine Inspection and Maintenance

When encountering this type of fault, it is recommended to perform troubleshooting in the following sequence: start from the exterior and proceed inward, then move from the pneumatic circuit to the electrical circuit.

• First, check the cleanliness of the air filter element and replace it if necessary.
• Next, listen for any distinct intake sounds at the intake valve, and check that the control air hose connections are secure and free of air‑leak noises.
• If the air circuit is functioning properly, disassemble and inspect the inlet valve assembly and the solenoid valve to verify their operational status.
• Finally, use a multimeter to verify that the pressure sensor and the control board are outputting signals correctly.