I posted this a couple weeks ago and am still looking for answers.
The problem I'm having is cold air out of the driver's side center
vent when set to mid-range temperature, e.g. 75F. If I run the set
temperature way up, e.g., 85F, it will route all air to the floor, and
it's warm. I've confirmed vacuum to the system, and the coolant hoses
to and from the heater are warm.

I have been searching old newsgroup postings and gotten several leads,
but so far nothing has fixed it or confirmed the cause. One or two
people have suggested an
error display sequence i.e., simultaneously pressing Off and Warmer
buttons to get codes to show up on the display. However, this doesn't
work on my car, something I today confirmed after subscribing to
AllData.
Only way to get the codes is with a scanner, which i don't have.
Also, someone said to momentarily disconnect the battery in order to
cause the AC programmer to reset. No help. I got a little better
understanding of the system from the diagrams in AllData, but it did
not
get me any closer to the answer. Perhaps I wasted $25 for the year's
subscription.

I have also pulled the passenger side under-dash trim and the glove
box
to get a look at the vacuum lines. They look OK to me.

Only thing I found that seems to be out of order is a discovery I made
with
my MiteVac tester. First, I checked the vacuum at the line going to
the reservoir
on the firewall. It reads almost 20 at idle, which I think is pretty
good. I then
on the tester on the line to a vacuum actuator on the drivers side of
the AC/heater
assembly. It reads around 17 or so when the temperature control is
very high (80F),
and drops off when I run the temperature back down. That seems to show
that
the programmer is working OK, at least to that actuator.

However, when I hook the tester to the actuator and pump it up, it
won't hold vacuum. If this
is a simple actuator I would think the diaphragm is ruptured. DOES
ANYONE KNOW
IF IT IS SUPPOSED TO HOLD VACUUM? If so, perhaps I've found my
problem.
Obviously I'd like to know for sure before trying to replace it, as it
doesn't look easy.

Any other ideas?

Thanks.

Ed

I don't have a PA and you didn't put what year, but maybe the system is
the same as my DeVille.

There are to motors/actuators for the air distribution system. One,
w/blue hose, for the AC-Def. One is a duel-diaphram motor, w/two
hoses-orange hose & tan hose. Orange controls air inlet valve, Tan
controls up-down valve. All vac motors must hold vaccum when tested at
the vac-motor port.

Dave S(Texas)

On 1/30/06 7:16 PM, in article
a%xDf.5668$2O6.2732 (AT) newssvr12 (DOT) news.prodigy.com, "Ed"
<jag_manR__EM*-0_V_E653 (AT) hotmail (DOT) com> wrote:


The actuator should hold vacuum. A small leak and it may still function. A
larger leak and it won't work at all.

It won't be. Dash removal will probably be involved. I've noticed that most
of the Haynes manuals I have don't detail the complete procedure either.


If there's heat from the other vent areas I would say you've found your
problem..

Dave,

Thanks for the reply.
Sorry, it's a '95. What year is your DeVille?

The one I am talking about is a dual. I noticed that but failed to
mention it.
In you car is the dual on the driver's side like mine?

How does that work? Do you mean there are two shafts coming out of
the motor,
each with it's own diaphragm?

I'm looking at the Air Flow diagram at AllData and can't quite match
my
symptoms to any failure mode I can see. Four doors (valves, as they
say) are shown:

1. Defrost-AC, which switches the air from center outlets to defrost.
2. Outside air or Recirculation, which switches inlet air between
inside the car and outside.
3. Air mix, which controls amount of air that is routed through the
heater core.
4. Mode, which controls the fraction of air going to floor versus
center outlets/side outlets/windshield

The main problem I'm having with this diagram is there is no door
shown would cause
the temperature coming out of the right side center vent to be
different from that of the left center vent.
It looks like any air going in the "up" direction as a result of the
positioning of door 4 will go to either the
side vents, center vents, or windshield, and all of these streams
should be at the same temperature.
Yet, when there is air coming out of the center vents the left one
issues cold air while the right
one issues warm air.

Is it possible that the diagram AllData is showing is not correct for
my car?


That's what I figured but didn't want to believe....

Thanks again.

Ed

"Michael Keefe" <keefemd (AT) frontiernet (DOT) net> wrote


Thanks, Michael. That's what I figured.

to get at
something in that area. I'll look it over.


Would you mind taking a look at my reply to Dave?

Thanks

Ed

I have now discovered OTHER airflow diagrams for Dual Zone AC, which
my car
has. These newly found diagrams offer explanation for my symptoms.
There are two
electric motors, separately controlling heater core bypass doors for
passenger and driver
side air. It looks like the one for the drivers side isn't working.
The car's in the shop
for other problems now, but I'll see if I can verify that when I get
it back. Unfortunately,
the controller motor is part of the HVAC programmer, probably a very
expensive part.

What I've learned from this is the stuff at AllData isn't organized
very well. One would hope to
see all applicable diagrams for the AC airflow doors in one place, but
also that isn't so.

Ed

On 1/31/06 1:31 PM, in article
g2ODf.28903$H71.15272 (AT) newssvr13 (DOT) news.prodigy.com, "Ed"
<jag_manR__EM*-0_V_E653 (AT) hotmail (DOT) com> wrote:

If you have air flow from both sides but the temperatures are different then
that is a mystery. On most cars the air is sucked from either the cabin or
the outside or both and blown through the AC accumulator to the mixing door
controlled by the rheostat (electric motor that runs the mix door). From
that point the air is directed either through the heater core, or bypassed
on to the ductwork. My only thought would be that the mixing door is not
completely closing one way when the heat is on and that air is taking the
easiest path through the ductwork (presumably to the left center vent). I
know that most AC systems seem to blow the air most forcibly out the console
vents and particularly onto the driver.

As for diagnosing this possibility, ... ??

Best of luck!

thanks, Michael. It turns out the car has a Dual Zone AC system, i.e.,
the
air to the drivers side is conditioned differently from that going
to the passengers side. I found AllData diagrams showing that. So now
it looks
the motor that is supposed to control the heater bypass for the
drivers side is
not doing it's job. Also, i think the actuator controlling
recirc/fresh is bad.

Ed

"Michael Keefe" <keefemd (AT) frontiernet (DOT) net> wrote