yeah, I see your point with them stubbornly and in a sneaky manner forcing a/c or cold air onto the windows. even if it's not manually in AUTO, it may still do its job. my Silverado, eg, will turn a/c on the very moment mode selector is even half way between floor and windshield WITHOUT A/C LIGHT COMING UP.
on my CR-V, I had all this bs disabled, there was a certain combination of buttons pressed simultaneously, that did it. I start looking into how to disable this feature on this car either.
yes, I, actually like Japanese cars ability to simply blow air through vents due to incoming air pressure. saves gas as you do not need to run fan. I have window visors, simply crack them open, and it naturally substitutes for fan.
but it has been around 26 lately, and that triangular vent kept blowing cold air, reflected from the driver window, and right into my face. got fed up with it.

 

hey, what's OAT? outomatic air temperature?

 

OAT, Outside Air Temperature.

 

oh, the ambient temp... gotcha... mutual terminology established.

 

yeah, I see where they might be coming from, with Toyota being a corporate sissy and lawyers telling designers how to make cars "suite proof".

YAHOO NEWS -- March 9, 2011 – General Motors Co is recalling recent Buick Lacrosse and Cadillac SRX vehicles due to a software defect that could disable the driver's ability to adjust the heating, ventilation and air conditioning.

GM said 10,179 vehicles for the model year 2011 were affected by the recall, which may prevent the defrost system from clearing the windshield.

The vehicles fail to comply with federal standards for windshield defrosting and defogging, the automaker said in a notice to the National Highway Traffic Safety Administration on Wednesday.

 

oh gods, I am really tired of Toyota's infinite - what's opposite to wisdom? - in it's desire to "know better" what is the best for me, lowly driver.
here's an interesting c/p from a guy who is like I am - I AM NOT STUPID, LET ME CHOOSE MY CLIMATE CONTROLS MYSELF:

Yeah, yeah, yeah... I know the party line: A/C=dehumidifier=no fog

And that works great when my windows are fogged on the inside... but what if I wanna use my windshield vent when they're not fogged (which is 90+% of the time)- I'm using the A/C unnecessarily, thus I'm using more gas. My comment was that, I cannot use windshield vents w/o A/C with the BASE manual system- but with the non-base AUTO climate control system it can be turned off. So the auto has more manual controls. How screwy is that!

Feel free to stop reading here, as the following is a bit of a rant.

My issue with this setup is not new:
In 2002, I sent an email to Toyota (re: my 99 4-Runner) about this issue, because that manual (even my 07 Camry's manual doesn't explicitly say it) doesn't state the A/C is on using this vent. It says something about "Fresh air intake", which Toyota has yet to give me a definition of what that actually means. This is based on many emails to Ask Toyota, from which I got MANY different, contradictory replies form them (it's off, it's on, it's this, etc). Oy!

This is one of their replies as to why it comes on:

"In the past we received many contacts from customers inquiring how to operate the front defogging system in the most efficient way. Because most customers were confused about the operation of the old (manual) design, we decided to link the air conditioning to the front defogger as this is the most effective way to defrost the windshield in the shortest period of time."
So because some schmuck didn't know how to defog their windshield (press the A/C button), I can't use the system as I'd like.

Sadly, 2 of my friends are the schmucks. I was driving with them (him & her)and their windshield fogged and they were getting nervous that they couldn't see anything. It went something like this:
Me: Turn on the air conditioner
Them: We don't want the cold
Me: Don't touch the temp, just press the button
Them: We don't want it cold
After a bit of annoying back & forth, they turn it on. And 10 seconds later:
Them: WOW! That's cool.
Me: OY!

b

 

Sorry, your friends are NOT SCHMUCKS, but just maybe you.....

Switching "solely" to A/C for defogging the interior surface of the windshield is like playing Russian roulette. It may work, it might not work at all, and lastly, the fogging condition might suddenly get MUCH WORSE.

1/ your "friends" are correct, almost all modern day systems will depend on the A/C's dehumidification capability for quickly (NOT!) removing the condensation. So, yes, you might, or might not, get DRY, DRIER, DRIED OUT airflow to the interior surface of the windshield using your method. But while mother nature has pretty much total control over the resulting dryness of the airflow, you can be sure that what WILL result is COLD airflow, typically 15-20F colder that the airflow just previously being used via the footwell outlets to keep the cabin heated to your desired level.

The bottom line....the only sure and certain way to defog, QUICKLY defog, the interior surface of the windshield is to use HEATING, turn the system to max heat and THEN switch to defrost/defog/demist mode.

In yesteryear, 20+ years ago, I would have advised the use of the A/C in conjunction with heat, but no more. These days once the A/C subsequently cycles off there will be a "ton" of condensate on the approximately 10,000 square inches of evaporator cooling vane surface. That moisture will now begin to evaporate into the incoming COLD fresh airflow, permeating the cabin, and you will now shortly be right back where you started, cabin super humid and a COLD windshield below dewpoint.