Unit stops cooling and displays E1 on the control panel; buttons may still respond but compressor will not start.

Safety first: Unplug the air conditioner from the wall outlet before removing any panels. Do not work on the unit while it is connected to power.

• Power reset: Unplug the unit for 5–10 minutes, then plug it back in and try again. Sometimes E1 can be a temporary sensor reading error.
• Access the front panel: Remove the front grille and filter. On many Black+Decker portable and window units, the room thermistor is clipped near the evaporator coil or behind the air intake grille.
• Inspect the thermistor: Look for a small probe with two thin wires going to the main control board. Check for broken insulation, corrosion, or a sensor that has fallen out of its clip and is hanging loose.
• Check connections: Follow the thermistor wires to the main PCB. Ensure the plug is fully seated and not corroded or burnt. Reseat the connector.
• Test the sensor (advanced): With the unit unplugged, disconnect the thermistor and measure its resistance with a multimeter. Compare to the service manual chart (typically 5–50 kΩ depending on temperature). If it reads open (OL) or 0 Ω, the sensor is defective.
• Replace if faulty: If the thermistor is damaged or out of spec, replace it with a compatible Black+Decker room temperature sensor. Route the new sensor along the original path and secure it in the clip near the evaporator intake.
• If E1 persists: After replacing the sensor, if E1 still appears, the sensor circuit on the main control board may be defective and the PCB may need replacement. This is best handled by a qualified technician.