Re: A/C recirculation/warm air from dash ponderings..

[Robert Houk - WorkGroup Server Firmware <Robert.Houk@East.Sun.COM>]

   > Depends. I *DO* want recirc when it's 99.9% RH outside. By default,
   > "A/C" selects recirc on some models (on '83 UrQ, it's forced, you
   > have no option; on '98 A4 it's selectable, forced on "max"). recirc
   > will dry the inside faster than non-recirc, almost always. But it's

   i must respectfully totally disagree.  maybe i don't if 'always' is dependent on 99%
   RH.  IME any other time recirc is typically the 'fog windshield' button.

Wow...I've never encountered a [car] A/C that wasn't capable of keeping
up with *any* internal humidity source (humans breathing, in particular).
Even my Ye Olde UrQe would easily dry out the inside of my car when it
is damp/humid/foggy/cold outside. The problem was it also *cooled* the
inside of the car. I want to go from cold and humid/clammy to cool and
dry -- that requires Heat and DeHumidifcation together. Lack of recirc
makes the system have to DeHumidify *more* rather than less -- under
*some* circumstances.

*I* am able to detect those circumstances. *I* am willing to manually
override the designers' *WRONG* default configuration/setting to get
*MY* desired environment. *I* strongly object to systems that *WRONGLY*
think they are more clever than *I* am in *ALL* cases. (I willingly
concede automatic systems generally fare better than manual control.
Just not always.)

My A4 *DOES* fog up the interior glass. It does this on automatic. It
does *NOT* give me any way to de-fog all the glass, other than to
crank up the heat excessively, manually force the fan on high, switch
on the rear defrost [time after time..., every few minutes as the
****ing automatic system that knows better than I do shuts itself off
again and again and again and...], and *OPEN THE ****ing windows. This
is demonstrable fact.  (I spent five hours driving up to ski country
in foggy rain, with the outside temp hovering around 37 degrees. As it
nudges 38, the A/C engages, and the inside dries out nicely, and all
the windows become nice and clear. As it plunges back down to 36, the
A/C shuts off, and the inside fogs over, and all the glassware goes
opaque. I spent *FIVE* hours experiencing this. I spent 4.75 hours
thinking of progressively more nasty things I would like to do the,
uh, humanoid creature(s) responsible for this travesty.)

My UrQ, for all it's HVAC failings, lets me solve this problem by the
simple expedient of running A/C max for a minute (AC forces recirc, by
the way! no option!), then running heat until the glass fogs up again,
iterate until trip is over. Tedious, but it works. One simple flick
of the temp lever (no sets of buttons to press 27 times in the correct
sequence...).

   > Obvious solution -- put the evaporator downstream from the heater core,
   > then when it's cold, you're blowing heated air over the evaporator, so
   > it won't ice up, just pull the moisture out of the air. Then you can
   > use the "A/C" to dry out the car even at 10F.

   except (my usual caveat: i don't know what i'm talking about) don't you have to cool
   the air below it's dew point to condense the water vapor?  and that dew point won't be
   changed by going through the heater, so you heat it up, only to cool it down again, and
   then you get nice frosty air in the cabin, right?

No more so that cooling it before heating it. You are pumping the same
amount of heat energy either way. It's "commutative", so to speak. I.e.,
add 40F then subtract 40F is the same as subtract 40F then add 40F.
Within reasonable limits.

   > The A4 is (according to my salesdroid) equipped with a variableschmariable
   > compressor which is always on, but load-varying, or some such thing.

   yeah, i know a guy with an A4 Avant who claims 'they fixed it, there's no power loss'.
   get this - he actually believes what the sales guy tells him.  i think (as you are
   alluding) it's salesdroid doublespeak-regurgitation of propaganda.

   when i hit the snowflake, the car bogs down.  maybe the load varies as it runs, but
   every clutched AC does the same thing really.

Yeah, my salesdroid (actually a pretty nice guy...) said just leave the
A/C always on, I'll never even notice it's there. BZZZT! WRONG. That
poor little ole 4-banger dragging 3000+ lbs of car around definitely
skips a beat when that ole snowflake icon goes down.

By the by, all of the above is not to say the A4 isn't a fine not-so-little
little ole car, just that it has its faults, and the automatic climate
control leads that list. "In fact", dominates that list. IMO, natch.

					-RDH