Diagram of HVAC Venting?

[Ti Kan]

David.Ullrich at ferguson.com writes:
> Is there only supposed to be a black plastic cover over the evaporator =
> (looks like it directs the drips to an opening in the firewall and has =
> air vents on it)? That's all that's separating mine from the cabin.

Yes.  That's the drain tray for the evaporator.

> I stick my head under there and hit the AC switch I can hear something =
> opening/closing and hear a difference in airflow (doesn't seem to make a =
> volume difference at the vents). So, I guess it is working properly. I =
> couldn't see anything move, should I be able to?=20

You're probably hearing refrigerant flow through the evaporator, not
changes in actual air flow.

> So, assuming that the venting system is working as designed, how do I =
> check the duty cycle of the compressor? How long/often should it be on? =
> How do I check whether the temperature control needs adjustment? How is =
> it adjusted? Sorry for all the dumb questions, but I'm not a good =
> mechanic...

I don't know what is the "correct" duty cycle, and it will greatly depend
on ambient temperature, etc.  However, the old (80-83) Bentley manual does
provide some guidance on temperature control adjustment.  Basically you
disassemble the center console, and make sure that at the coldest
setting of the temperature lever, it also concides with the maximum
position of the temperature switch that is attached to it.  If not, then
you loosen two screws and rotate the switch until it does.  Quite a
pain to do.

-Ti
01 S4 2.7 biturbo quattro
84 5000S 2.1 turbo
80 4000 2.0
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