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

[Wallace White <wallace@remdesign.com>]

Benedikt -

I believe the ducting and flaps are the same for all 5k's ('84-'88;
don't know about '89-'91), even though the climate control head and
programmer changed.

The climate control head (at least the digital one, '86+) will set the
intake to recirc when off, as you said, and when it's really trying hard
to bring the temperature down. Set it to AUTO and LO temperature, and
the recirc door should open. Most of the time, it does set the intake to
fresh air. Some people would rather have more control, but then other
systems that give more control are often used improperly. How many times
have you been riding in a car with someone and the windows kept fogging
up? There's a big tradeoff between giving the user control and, well,
making the system work well for the average user.

If you were to modify the system to give you control of the recirc flap,
keep in mind that that vacuum solenoid also triggers the heater valve.
When the solenoid is energized, the door moves to recirc and the heater
valve closes, keeping the coolant from running through the heater core.

Yes, the system would still work if you controlled that door. It's
really two doors: one that covers the fresh intake, one that covers the
recirc intake. The doors are physically connected by a bracket, and the
whole assembly pivots back and forth so that one door is open and the
other is closed. The spring or the bracket for the vacuum piston often
breaks, leaving the thing stuck in recirc or fresh, respectively. And
the vacuum line can fall off of the piston, making the whole system lose
vacuum (i.e. defrost only) when the head opens that vacuum solenoid.

The Bentley describes and depicts all this in many, many pages, with the
diagrams you may be looking for.

- Wallace
  '87 5kcstq 152k

"G. Benedikt Rochow" wrote:
> 
> I've got an '84 5kS, but these thoughts and questions probably
> apply to a number of models.
> 
> I'm guessing that I'm not the only one to be slightly annoyed
> by the presumption that I always want "fresh" air when I want
> heat/cooling, as well as no warm air from the dash vents.
> (Tangent: I noticed that Steve Cobram's early US V8 brochure shows
> the same climate control unit, and a separate recirc. button that
> nobody appears to have. I remember that when the just-superseded
> MB S-class came out, the recirc. switch on the climate control
> was touted as a big-deal feature; maybe Audi was toying with
> this revolutionary idea...even my mother's mid-70s Renault 4 had
> a continuously-variable inside/outside control on the heater.
> But I digress.)
> So, besides putting in switches to override the A/C head
> unit's idea of where the air should go to,
> I'd like to bring my A/C up to the standards of a
> lowest-model Renault designed in '61 :) with regard to "fresh" air:
> 
> BIG Question: Is the way the air is routed such that it would
> work at all to have the recirc. flap open and the fresh air
> flap closed, or is "fresh air" the only intake for the blower
> motor?
> (Considering that I don't know of a mode other than 'off' that
> uses recirc. air - is that correct? - I'd guess it doesn't
> work. Considering that there's a recirc. flap at all, I'd
> guess that the 'knowledge' above is incorrect, as there would
> be no point in having it otherwise, right?)
> 
> any ideas/knowledge/experience?
> (diagrams? :)
> 
> thanks,
> -gbr