I have no idea what this switch does. Says ‘FACE’ on it but it seems to do nothing. Looks like hot and cold but it doesn’t seem to do anything.
Please excuse my undetailed console…
Thank you!
Solo out…
You always want the cooler air to your face, it’s a tiny adjustment to the AC that seems to do very little. There is a blend flap on the other end but it’s not effective. Not sure who wants a hot head and cold feet.
So, if the left triangle is air to the face, what is the triangle to the right that is red?
in ht weather, I like the AC to blow to my face.
In cold, it works to direct warm ar that way, for defrst to the windshied.
My feet are rarely cold, in cold weather, i wear warm foot gear.
European manufacturers always had a thing for that control, I know BMW and Mercedes had them, likely others. Most climate control systems once stabilized in the winter will default to heat down low and less heat up front to keep from drying out your eyes and such. Far as I recall that blend lever will let you adjust how much cooler the upper blown air is.
If you wait for the system to stabilize in ‘blend mode’ you can feel a difference. Subtle. But it’s there.
TBH I usually forget the control even exists. I remember in August. 
Cheers
DD
Both triangles refer to air coming to the upper outboard outlets. Blue is (a tiny bit) colder, red is (a tiny bit) warmer. The control doesn’t do anything besides that.
Cheers
DD
I always thought it was just a pretty impressive-looking “do nothing” … but it sounds like it does in fact have some effect on the HVAC system operation … 
It’s a bias adjustment.
Warm head (cold feet) or
Cool head (warm feet).
In the e38 and surely other BMWs you really feel the difference…
David, the adjustment doesn’t work quite like that. Not on my car, at least.
The lower temperature isn’t changed at all. Just the upper.
From my owners manual:
“The thumbwheel control, located in the radio panel, can be used to alter the temperature being distributed through the face level vents.” [italics mine]
Cheers
DD
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Okay, but colder air to the face would mean the temperature out of the other vents would have to be increased to compensate so that the general cabin temperature stays the same. That means the feet must get warmer air when the face level blows cooler.
Theoretically of course!
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What you say makes perfectly good sense, actually. But, like the adjustment itself, the change is probably very slight so I’ve never noticed.
Cheers
DD
O.K., I guess the only way to get to the bottom of this “issue” is for someone with a thermometer (preferably one of those “laser pointer” types) to test the temp at all 4 vents with the slider knob all the way to one side and then all the way to the other side (and pointed at the floor vents, as well 
). 
Any volunteers? 
You!
………10
Mercedes back in the 80’s had a wonderful special tool that had a temp probe for each vent and a unit that displayed all the info, there was a procedure to go through to insure correct functioning of the system, rate of temp change, etc, etc. Good stuff…
Not me … some cad made off with my laser thermometer some time back … 