Crane ultrasonic humidifier shows E4 and the mist output is disabled.

Safety first: Unplug the unit and remove the water tank. Never run the humidifier without water to test the transducer.

• 1. Inspect and clean the transducer:
  • Locate the round metal ultrasonic disc in the base.
  • Use a 1:1 vinegar and water solution and a soft cotton swab to remove mineral deposits.
  • Rinse with clean water and dry with a lint-free cloth.
• 2. Check for physical damage:
  • Look for cracks, pitting, or discoloration on the disc.
  • If the disc is cracked or warped, it must be replaced.
• 3. Inspect wiring:
  • Open the base (if comfortable) and trace the two wires from the transducer to the control PCB.
  • Ensure connectors are firmly seated and wires are not broken or corroded.
• 4. Test after cleaning:
  • Reassemble, fill the tank, and power on.
  • If E4 persists and there is no vibration or mist from the disc, the transducer or driver circuit is defective.
• 5. Replace parts as needed:
  • Replace the ultrasonic transducer module if available as a spare part.
  • If replacing the transducer does not resolve E4, the main control PCB/driver board will likely need replacement.