Display shows F1 and the unit may not cool or may run erratically.

Safety: Unplug the air conditioner before removing the front cover.

• Locate ambient sensor: Remove the front grille and filter. The ambient sensor is often positioned near the air intake behind the grille, separate from the evaporator coil sensor.
• Check mounting: Ensure the sensor is not touching cold metal surfaces and is positioned in the airflow path. Reposition if necessary.
• Inspect wiring: Follow the sensor wires to the display or main PCB. Look for breaks or pinched sections. Reseat the connector.
• Test sensor: With the unit unplugged, disconnect the sensor and measure resistance. Compare to the expected value at room temperature. Replace if open, shorted, or out of range.
• Replace sensor: Install a compatible Black+Decker ambient thermistor, route wiring as original, and secure it away from moving parts.
• Board check: If a new sensor does not clear F1, the control board input may be defective and require replacement.