Display shows E3, compressor will not start or shuts down quickly.

Safety: Disconnect power before servicing. The condenser area may be hot after recent operation.

• Access condenser: Remove the rear or side panel to expose the hot condenser coil (the coil near the exhaust outlet on portable units).
• Find the sensor: Look for a thermistor clipped or strapped to the condenser tubing or fins with two wires going to the PCB.
• Check attachment: Ensure the sensor is firmly in contact with the coil. Re‑clip or tape it securely if loose.
• Inspect wiring and connector: Look for heat‑damaged insulation, melted clips, or loose connectors. Re‑seat the connector on the main board.
• Measure resistance: With the unit unplugged, test the sensor with a multimeter. Compare its resistance to the evaporator sensor at similar temperature. A reading of 0 Ω or infinite indicates failure.
• Replace sensor: If faulty, install a new Whynter condenser temperature sensor and route the wires away from the fan and hot discharge lines.
• Control board: If E3 persists with a known‑good sensor, the main control PCB may be defective and require replacement.