AC is "on" when turned "off"?
 

I have noticed that when I turn my AC off, but my temperature to "coldest" I can still feel AC coming through windshield vents in the "windshield-vent" mode. When I turn the vent dial mode to other vent modes, I do not feel the AC anymore.

Yes, I'm sure it's AC coming through in windshield-mode. How do I know? In windshield mode, it's super chilly air, "AC-like". In every other vent mode, it feels like "normal" air, that isn't chilly.

Why is this happening? I have no idea, I would think AC and vent controls are not interconnected.

This concerns me, because I don't want to burn up extra fuel to support AC when I don't necessarily want AC. I haven't taken this in yet, but I wanted to see if anyone else could recreate this also.

When you set your selector to any setting that includes the windshield, A/C automatically comes on. Most newer cars do this.

Hmm... I'll have to check my '11 Forester XT, but I had a '11 Ford Fusion, and I don't remember it doing that.

It's designed to defog the front windshield. Newer Toyotas do that.

got the same on my 07' 350z, most newer car do this. However, its also noted in the Drivers Manual, so RTFM :-)

You might be able to deactivate this by holding certain buttons on the A/C unit, and/or turning the key to a specific setting.

It will take time before anyone learns these codes though, eventually someone will post them if it's possible. It worked for my Acura, now I decide when the compressor comes on. Actually it still works as designed, but now I have the ability to turn it off by pressing the button.

So, where do these little bits of knowledge come from? Shop manuals? Service manuals at the dealer?

I'm sure you can "disable" it by setting the temperature to a bit warmer. That's what I do in my GTI...

My NC MX5 automatically turns on the AC (if switched off) when I set it to defog the front windshield.

A/C mode turns on when used for defogging because a/c air has less moisture in it than regular cabin air.

Even with the heater the AC system will run in a defog setting.

Most, if not all, new cars do this as already stated. In many cars you can easily disable it, in some, it requires a bit more work.

atleast you have a premium so you have more control over when the a/c comes on vs the auto climate control in the limited models.

The AC runs because it also removes humidity from the air.
Humid air on windshield = fog.

So if the compressor is running this often, then the car will be a bit down on power, because it's a tiny 2.0L engine and electrical stress does this.

What's the easiest way to knowingly turn off the compressor?

Just don't set it to any setting that shows the windshield/defrost on the dial.

Both of my other newish cars did the same thing.