I have an Air-O-Swiss 7135 Humidifier. The empty indicator light stays on even when the unit is full, which prevents the unit from operating. There is a float-type device that appears to be the part that is supposed to allow operation. I tried the troubleshooting procedures in the booklet, but to no avail. Any suggestions short of complete disposal?

Its probably the cleaning light that comes on periodically to remind you to clean the unit. Shut off the unit AND when you do so hold down the power button for several seconds until the flashing red light shuts off. The cleaning light should stay off until the next cleaning is due.

Per the Air-O-Swiss FAQ:

Q: Cleaning light is flashing (AOS U650, AOS 7135, AOS 7142, AOS 7144, AOS 7147)
A: Switch the unit OFF and unplug it. Empty the water in the base. Rinse the base with hot/clean water. Do not submerge the base! Visually inspect the base for dirt or mineral build up. If soft water is used decalcifying the unit every 4 weeks with EZ Cal is suggested. If hard water is used the unit should be decalcified every 2 weeks. Do not forget to reset the clean light after resetting the unit.

Q: Reset cleaning light (AOS U650, AOS 7135, AOS 7142, AOS 7144, AOS 7147)
A: The cleaning light does not automatically reset. Hold down the power button (button A in instruction manual) until the light stops flashing. The light automatically comes on approximately 14 days after plugging in the unit.

The water sensor is a float in the mister area of the base. The float is off in one corner with a little plastic barrier around it and translucent cap over it. Make sure the float can more freely. If the float can move up and down but the light stays on, the reed switch (a switch controlled by a magnet built into the float) inside the unit might have been knocked loose, damaged or disconnected. The switch is actually inside the post that the float slides on, but it can only be accessed from the underside - inside the unit.

These hints are from the air o swiss webpage.
Q: No mist / unit is not working / empty indicator keeps flashing
A: Fill up the water tank. Check if water is flowing through the demineralization cartridge (attached to the water tank cap). If the water tank is full but there is only little water in the base it indicates that the water is now flowing through the demineralization cartridge.

• Wait for 15 minutes to allow the mist to come out of the unit.
• If the unit is not working and the empty light is not flashing you might have set the desired humidity too low and the current humidity level in the room is higher. That is why the unit switches off automatically.
• If the empty indicator continues flashing and the tank is full, water is not flowing through the cartridge. Exchange the cartridge or the granules in the cartridge after 2-3 months, in areas with hard water exchange the cartridge after 1 -2 months. However, the demineralization cartridge and or the granules must be exchanged at the latest after 6 months or the unit does not reach its full performance.

If the granules are new, see the following instructions:

• Make sure the cartridge and/or granules were soaked for 24 hours, water takes longer to filter through dry granules in cartridge and into the base. Next, remove 2 tablespoons of granules from the cartridge, and throw them away. Too many granules in the cartridge it does not allow water to flow from the tank to the base.

If your issue is with the float and not the mister, then you have to make sure the float is tripping the micro switch that turns the machine on. Some units the filter will not allow the float to hit the switch if the filter is not installed correctly. If everything is in correctly and the float is tripping the switch, then the micro switch must be faulty.

Gererally according to the booklet in the box.
If you no longer have those instructions, simply clean out the
basin, make sure no mold, dust, hardwater or calcium is deposited.
Use a 10% bleach water solution to kill bacteria, and thats is basically it.
Just dont miss any spots, but humdifiers should be cleaned every few uses.

no its not a problem if you dont mind how the system looks...otherwise just get some oil paint and re-coat it

When you cleaned it , did you remove water level sensor? If so did you put it back in upside down? The sensor is a plastic cylinder that is held down by a screw and washer.. If you have it in upside down, the empty water red light will be lit,,, if you unscrew the sensor and flip it .. it should start to work again..

Here is the general download page for all AOS manuals and quick set-up guides.

Here is the direct link to the AOS 7135 manual in pdf format.

would you describe your problem in a little more detail please?

I had the same problem. I replaced the filter and cleaned the base and then it worked.

sounds like the filter is not allowing air flow.