[s-cars] Blower squeak

[Joshua van Tol]

Yeah, but look at what their line of sight is. They typically have a  
30 degree code that they look at. Basically, think of it as an  
averaging thermal imaging camera with about a 30 degree wide field of  
view.  Those sensors work exactly the same way as a non-contact infra- 
red thermometer.

I'm not saying they don't work well, they do, but they have their own  
drawbacks, and they're not the same ones as air temperature based  
systems.

As for the coffee cup thing, typically there's a filter algorithm to  
remove the effects of a short duration step input (drinking from your  
cup of coffee) but if you're in the small minority of drivers that  
holds a cup of coffee in front of them while driving (and these  
people do exist), and the sensor's field of view hits the cup (and it  
usually will, because by hitting the driver, and the driver's  
immediate surroundings, the algorithm is usually easier to tune) then  
eventually you'll notice the system trying to cool you off because of  
that hot coffee. You have to be looking for it, and it's a minor  
thing that affects a very small population of drivers, but it is real.

On the other hand, what you're referring to as an IR sensor may in  
fact be a sun sensor (which sometimes  is called an IR sensor,  
because it's usually designed to be more sensitive to infra red vs  
visible light). In which case, there's still a temp sensor (or a true  
IR sensor) somewhere in the cab, you just haven't found it yet.  
Oftentimes they use a small grille on the front of the climate  
control head unit, and there may be a small fan, or some clever  
manufacturers use a venturi tube from the blower fan assembly to draw  
air across the sensor.

Actually, given your description of this sensor, I think it's much  
more likely that it's a sun sensor. If it has a little frosted  
plastic globe over it, then it's a sun sensor. If it has a small  
aperture, with a matte black lens at the back of it, then it'll be an  
IR sensor.

Many late model Chrysler vehicles use IR sensors, and on those  
vehicles, the sensor is often mounted on the A-pillar, in the  
overhead console, or right in the climate control head unit itself.

On May 24, 2007, at 1:35 PM, Taka Mizutani wrote:

> Re: IR sensors for climate control adjustment
>
> I don't know what car you're referring to, but in both the V70 and  
> the Impreza, the IR sensors are at the base of the windshield, far,  
> far forward and pretty much out of reach. No interference from any  
> hot coffee IME. In all seriousness, I've never seen the effect that  
> you mention.
>
> Audi has gone to IR sensors in the dash as well- I haven't seen one  
> of those little air intakes on the dash since the C4 generation.
>
> Taka
>
>