Unit stops cooling and displays E1 on the control panel; buttons may be unresponsive until power is cycled.

Safety first: Unplug the Arctic King air conditioner from the wall outlet before removing any covers. Capacitors inside can hold a charge; avoid touching exposed terminals.

Steps to check and correct E1:

• Power reset: Unplug the unit for 5 minutes, then plug back in and try again. If E1 returns, continue.
• Access the front panel: Remove the front grille and filter. On many Arctic King window units, the room temperature sensor (thermistor) is clipped near the evaporator coil or behind the air intake grille.
• Inspect the sensor: Look for a small probe with two thin wires going to the main control board. Ensure it is firmly clipped in place and not touching the coil directly or dangling in free air.
• Check connections: Follow the sensor wires to the control board. Reseat the connector by unplugging and plugging it back in. Look for corrosion, broken insulation, or pinched wires.
• Test the sensor (if you have a multimeter): With the unit unplugged, disconnect the thermistor and measure resistance. At room temperature (around 77°F / 25°C), many Arctic King thermistors read roughly 8–15 kΩ. A reading of 0 Ω (short) or infinite (open) indicates a bad sensor.
• Replace if faulty: If the sensor is open/shorted or physically damaged, replace it with an Arctic King-compatible room temperature sensor (thermistor). Route the new sensor wiring along the original path and secure it away from sharp metal edges.
• Board inspection: If a known-good sensor still triggers E1, the main PCB sensor circuit may be defective. Inspect the board for burn marks or corrosion. Replacement of the main control board is typically required and may be best handled by a technician.