Dehumidifier displays E4 and shuts down; compressor does not run and unit will not dehumidify.

Safety first: Unplug the dehumidifier. Allow any ice on the coil to melt before working near it.

• Allow full defrost: If the unit was operating in a very cold room, move it to a warmer area (above 41°F / 5°C), unplug it, and let it sit for several hours to fully defrost. Then restart and see if E4 clears.
• Locate defrost sensor: On many Hisense models, the defrost sensor is clipped to the evaporator coil or suction line. It may be bundled with foam insulation.
• Check attachment: Make sure the sensor is firmly attached to the coil or tubing and not hanging loose. Re-secure with the original clip or metal clamp.
• Inspect wiring and connectors: Follow the sensor wires to the main PCB. Look for broken insulation, pinched wires, or loose connectors. Reseat the connector.
• Replace sensor if needed: If the sensor is physically damaged or tests open/short with a multimeter, replace it with the correct Hisense defrost/coil sensor.
• Board-level issues: If a new sensor does not resolve E4, the main control board's defrost circuit may be faulty and should be replaced by a professional.