Re: type 44->a6/100 CC update info(long, but worth it!)

[Chris Newbold <newbold@telerama.com>]

Brett Dikeman wrote:

> -Vacuum system is different, but against what some listers said months ago,
> the a6/100 system is NOT completely electrically -ACTUATED-.  It is
> electrically -CONTROLLED-(as is the type 44.)

I hate to rain on this, but I believe that it *is* fully electrically
actuated, with the exception of the recirculation flap. While I don't have a
service manual, here's the evidence I have from the climate control in my
1993 90 (which uses the same system as the similar vintage 100/A6):

- it sounds electrically controled: adjust the temp, and you get a "bzzzt"
  from the flap motor; most dramatic is to go from full hot/cold to the
  other end: it takes about 8sec. for the motor to crank the flap into
  place; you can hear continuous adjustments too: "bzzzzzt" "bzt" "bzt".

- diagnostic data: CH8 is "digital value of temp. regulator motor pot.";
  CH11 is "digital value of central flap motor pot."; and CH13 is "digital
  value of footwell/defrost flap motor pot."

- more diagnostic data: trouble codes can indicate that any of these
  three flaps have become stuck; notes say that the head tries to free
  the flaps by cycling them repeatedly from one extreme to the other.

- still more diagnostic data: another channel shows control head electrical
  ouputs; if you make changes to temp or airflow, you can see continuous
  outputs to the various flap controllers until they're in the right
  position, then just small "tweaks"

- fan speed: the fan speed appears to be "infinitely" variable; in fact,
  it seems to have about 16 discrete steps, represented by and LCD bar
  graph; I don't know how they achieve this fine control, but I doubt
  that it's with resistor packs... (though in theory, it could be!)

-Chris
1993 90CS 71k miles