That’s it. I guess if it says “fan only” it must not be doing it. But I wonder if it’s more complicated.
Even if my heat is set to high, my windshield defogs almost immediately when I turn the air conditioning on.
Air conditioners dehumidify by dropping the air temperature when it blows across the cooling coils. If it’s not cooling, it’s not dehumidifying.
The A/C is still cooling, the system is just mixing the cold dry air from the A/C with hot air from the heater.
No, it doesn’t. If it’s not set to cool (or heat) and you move the fan switch from auto to on, it’s just a fan, nothing more. If this is a central AC, it’ll still help to circulate the air in the house, and technically it’s filtering it as well, but it’s not going to dry the air. You can verify this for yourself by watching the drain. No water will drip out if the refrigeration cycle isn’t happening.
The temperature is (kinda) irrelevant to the humidity of the air you’re blowing over the windshield. Blowing warm, dry air is going to be better than just recirculating the same air over and over without dehumidifying it. The condensation on your windshield turning back into vapor and the humidity from your breath needs to be removed.
My humidity inside was 14 a couple days ago, and it’s 74 at the moment.
I think mini splits are able to keep the average temperature constant while dehumidifying.
The way they do it is that when set to “dehumidify”, they cool in bursts, then change valve positions and heat in a burst to warm the air back up as much as the cooling took away. The heating doesn’t add humidity, while each time during cooling, the condensate water is dripping into the drain pan and exiting the building.
Nitpick
Some mini splits some mini splits will not. Depends if it is a heat pump or not.
If the compressor is running it is dehumidifying (except when used as a heat pump, which would be for homes that can heat using the a/c, not for cars). Now if the compressor is running is up to how it is set up. In a car if the a/c is ‘on’ the compressor is running, or at least cycling on/off, any heat is provided by a separate system, so yes in a car (as long as the a/c system is working).
In a window unit, normally the compressor is not running if the temperature is set too high for it to activate it, unless it has a dehumidify setting which will cycle the compressor on for a short time even if the temp is low enough. For central a/c’s it can get more complicated depending on how it is controlled, but the short of it is if the outside fan (which also the compressor is running when that runs) is running then yes it should dehumidify. For heat pumps the mode must be set to cool (or doing cooling), which means that the outside fn (and compressor) is running and the coils are warm and the outside unit is blowing hot air.