You might need to check either the water level sensor or make sure that there aren't any deposits on the nebulizer. I just posted the following sections from the manual for another problem:
According to the Crane's Troubleshooting section:
The power light is green but there is no mist being emitted:
- Check that there is water in the tank.
- Check for possible lime deposits on the water level sensor or the nebulizer.
- Make sure that nothing blocks the vapor output slots.
- Check that the fan vent on bottom of humidifier is not blocked.
- Empty the humidifier and rinse the water basin with cool tap water and allow to dry for 15 to 30 min.
Humidifier power light is staying red and not turning green. Or, Humidifier is working then stops:
- Ensure that water level sensor is assembled properly. (I scanned a page from the manual that shows how to dismantle and reassemble the sensor: here
- Clean water float.
- Call service center and request replacement water float.
Barring that, here is the service center contact info:
Dart Warehouse Corporation
Tel: 1-888-599-0952 (Business hours Mon-Fri 9:00 am - 4:00 pm Ct)
1835 Ferry Road
Naperville, Illinois 60563