Compressor does not start; display shows E3 after a short delay.

Safety: Unplug the unit. The compressor and discharge line can be very hot; allow the unit to cool for at least 20–30 minutes before touching internal components.

Steps:

• Allow cool-down: If the unit has been running hard in high ambient temperatures, let it cool and then restart. E3 can sometimes be triggered by temporary overheat.
• Access compressor compartment: On portable units, remove the rear panel; on window units, remove the outer shell. Locate the compressor (black metal can) and the small sensor clipped to the hot discharge line.
• Inspect sensor and wiring: Look for melted insulation, loose clips, or wires touching the compressor shell or fan blades.
• Test sensor: With a multimeter, measure resistance at room temperature and compare to specifications or to another similar NTC sensor in the unit. Replace if open or shorted.
• Check airflow: Verify that the condenser fan is running and that the rear exhaust or condenser coil is not blocked with dust or placed too close to a wall. Poor airflow can cause real overheat and repeated E3 errors.
• Replace parts as needed: Install a new compressor discharge temperature sensor if faulty. If the sensor is good but E3 persists, the main control PCB may need replacement.