What does F mean on aircare humidifier? what does CF mean?

From what you've described, it seems that the "A" setting may be a special or additional mode of operation. It could be an "Auto" or "Adaptive" setting that adjusts the fan speed based on the humidity level in the room, or it could be a specific function designed for a certain type of room. I recommend checking the owner's manual or contacting the manufacturer directly to find out more information about the specific function of the "A" setting on your Aircare (Valiant) Humidifier HD1409.

Question edited for a lot more clarity.

Manual and Parts Diagram

https://www.appliancefactoryparts.com/content/pdfs/215203-1.pdf

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empty tank unit shuts off until tank empty

clean filter, filter is blocked not letting the air flow through correctly, take the filter out and clean it with warm water and leave to dry before refitting, can use soak but not to much as can damage the filter threads. but warm water will do the job to remove the particles its picked up.

Check Filter Indicator The ability of any humidifier to efficiently supply humidity output relies heavily on the condition of the filter. As the filter loads with impurities it gradually loses its wicking capability. When this happens, moisture output is reduced and the humidifier has to work longer to satisfy the selected setting. This humidifier has a check filter reminder timed to appear after 720 hours of operation. When the Check Filter (CF) message is displayed, disconnect the power cord and check the condition of the filter. If a build-up of deposits or severe discoloration is evident replace the filter to restore maximum efficiency. The CF message is reset when the humidifier is plugged back in.

Depending on your model, the CF could mean the filter needs to be changed or that the unit needs to be reset. If your model doesn't have a reset button, you can unplug the unit from the outlet for 5 minutes.

If it has a humidistat in the power cord it may have gotten wet when refilling. Blow the water out, or remove the screw to open the small casing and dry it out. If it was wet, the unit should start running normally.

It may mean "Change Filter." After you replace the filter, unplug the humidifier for 30 seconds, and then you plug it back in, the CF code should be gone.

It means Change Filter.

However, assuming that you have done that in the recent past, you probably want to know more. I'm not sure how this actually works (that is why it shows CF). I saw it for the first time after 2 or 3 years of using my humidifier. (And I had just changed the filter a week or so previously).

You may have to turn the unit off/on or even unplug it to clear the message, then it should operate normally.

CF means CLEAN FILTER