Display shows E4 and the unit stops cooling; may beep and shut down after a short run time.

Safety: Disconnect power. Do not bypass any thermal protection devices; they are critical for fire safety.

• Check airflow: Inspect both intake and exhaust vents. Clean any dust buildup on the front filter and rear condenser grille. Ensure the exhaust hose (portable units) is not kinked or blocked and is properly vented outside.
• Clean condenser coil: Remove the rear panel or outer shell to access the condenser coil. Use a soft brush and vacuum to remove dust and lint from the fins. Do not bend the fins.
• Allow cooling: If the compressor was very hot, allow the unit to sit unplugged for at least 30–60 minutes to let the internal overload reset.
• Inspect temperature sensor: Locate any sensor clipped to the compressor shell or high side line. Check for loose mounting or damaged wires. Reseat connectors on the main PCB.
• Restart test: Reassemble, plug in, and run the unit on COOL with proper ventilation. If E4 returns quickly under normal conditions, the high-temp sensor or control board may be defective.
• Replace sensor if needed: If you can identify a separate compressor temperature sensor and it tests open/shorted with a multimeter, replace it with a compatible Black+Decker sensor.
• Technician recommended: Persistent E4 after cleaning and sensor replacement may indicate compressor or PCB issues that require professional diagnosis.