Display shows E4 and compressor does not start.

Safety warning: Refrigerant circuits are pressurized. Do not attempt to open the sealed system. Only qualified refrigeration technicians should handle refrigerant. You may, however, safely inspect electrical connections and airflow.

Steps:

• Power cycle: Unplug the unit for 10 minutes to allow internal protections to reset. Plug back in and check if E4 reappears.
• Clean condenser: Remove the rear or side panel to access the condenser coil (warm coil). Use a soft brush and vacuum to remove dust and lint. Ensure the condenser fan is unobstructed.
• Check airflow: Verify that intake and exhaust grilles are not blocked and that the unit has adequate clearance from walls.
• Inspect pressure switch wiring: Locate the high/low pressure switch or pressure sensor on the refrigerant line (usually near the compressor). Check the two- or three-wire connector for secure fit and no corrosion or damage.
• Reset and test: After cleaning and checking connections, reassemble, restore power, and run the unit. If E4 persists, the pressure switch or sealed system may be faulty.
• Call a professional: If the error remains, contact an authorized Argo service center. The Argo pressure switch / pressure sensor or sealed system may require replacement and refrigerant handling.