Dehumidifier shows E4 and shuts down or will not start

Safety: Unplug the unit before opening. Do not attempt sealed system (refrigerant) repairs unless you are EPA-certified.

Steps to troubleshoot E4:

• Allow coil to thaw: If the evaporator is iced over, turn the unit off and let it sit unplugged for several hours until all ice melts. Place towels under the unit to catch drips.
• Clean air filter and grille: Remove the bucket and pull out the air filter. Wash with mild soap and water, dry completely, and reinstall. Vacuum dust from the intake and exhaust grilles.
• Check room conditions: Ensure the unit is used in a room within Whirlpool's specified temperature range (typically 41°F–95°F / 5°C–35°C). Very cold rooms can trigger E4.
• Inspect evaporator thermistor: Access the coil and verify the thermistor is firmly attached and wiring is intact (see E2 procedure). A loose or faulty thermistor can misread coil temperature and cause E4.
• Restart and observe: After cleaning and checking the sensor, run the unit. If the coil quickly ices over again and E4 returns, there may be a sealed system problem (low refrigerant, restriction, or weak compressor).
• Do not attempt refrigerant recharge yourself: Sealed system work requires specialized tools and certification. If airflow and sensors are good but E4 persists, contact a qualified technician to evaluate the sealed system.

Test: After cleaning and sensor checks, confirm that the unit runs for extended periods without E4 and that the coil frosts lightly and evenly, then defrosts normally.