Safety: Unplug the unit before removing any covers. Avoid touching the sharp fins of the evaporator coil.

Steps:

Access the evaporator: Remove the front or rear panel to expose the evaporator coil (cold coil). The evaporator sensor is usually clipped or taped to the coil tubing.
Check sensor placement: Ensure the sensor bulb or bead is firmly attached to the coil surface. If it has fallen off, reattach using aluminum tape or the original clip.
Inspect wiring and connector: Follow the two-wire harness back to the main PCB. Look for nicks, pinches, or loose connectors. Reseat the connector on the board.
Measure resistance: With the unit unplugged, disconnect the sensor and measure resistance. Compare to the ambient sensor; values should be similar at room temperature. A reading of 0 Ω or infinite indicates a failed sensor.
Replace sensor: If faulty, install a new Bionaire evaporator temperature sensor with the same connector and rating.
Board replacement: If a new sensor does not clear E3, the main control PCB is likely defective and should be replaced.

Dehumidifier displays E3 and will not start dehumidifying

Possible Causes