I don't believe there is a way to control the air flow in 94-99 Devilles. Mine blows A/C out of dash vents and heat out of floor vents with defrost. Other Devilles did the same thing so I'd say it's default.

I also had the "automatically switching" air flow problem 2 years ago, air started to come out of defrost when the car goes over 45mph. Turned out to be a vacuum problem at the parking brake diaphragm. With the vacuum leak it wouldn't release parking break when I put it in gear.

 

GM probably was stoned when they thought automatic vent control was a good idea. I remember it took me a week to realize that I can't control the vents when I first bought my Deville.

I'm pretty sure I have a vacuum problem because on the passenger side firewall there's a small black plastic hose that goes into the cabin along with a bunch of wires, it's a vacuum hose except it seems to be blocked because no air can go in or out of that tube when I tried to blow and suck with my mouth(god that sounded bad). That would explain my AC blowing out of the defrost in the summer.

I could say, disconnect the actuator and have the heat and AC permanently blow through the dash and floor vents, but I'll have to tear apart the whole dash and that ain't gonna happen anytime soon.

 

Yeah I hate this "feature" as well. Why couldn't we just select where we want it to blow out? It is designed to blow heat out the defrost and floor when its on max heat. But if you are something like 8 degrees from the ambient outside temperature, then it will blow through the vents. But most likely depending on where you live, its probably gonna be cold or cool air blowing on you with low outdoor temps right now. On my 94 deville 4.9 I have some funky air door problem but no codes where the heat is cool/warm on the driver and hot on the passenger. So I just switched the red and the yellow(?) vac lines on the door actuators to get it to blow out the dash all the time. I hate working inside the dash. I hate trim in general. It breaks so darn easily. I haven't looked at the 97 deville yet to see if that would be possible if I had the same issues. So far it is working, "as advertised."

 

I miss the superheated air hitting my face when I drove around in a Geo Metro many years ago :cool2:


Are the 2000+ Devilles the same way? How about the 94~99 Deville Concours, I think those have buttons in the center console to select where you want to direct the air to.

 

Are the 2000+ Devilles the same way? How about the 94~99 Deville Concours, I think those have buttons in the center console to select where you want to direct the air to.

The Devilles got a mode button in 2000 so you can control where the air is distributed from. Not sure about the Concourse.

 

There's supposedly a way to override that and force the heat out the center dash vents.

I've posted the procedure here before.

Personally, I don't like heat blowing on my face. I can't breath.

 

How to get heat from your 90's De Ville center vents or getting heat when nothing else works due to a vacuum leak (no cruise control or brake release ability usually indicates a vacuum leak):



Enter Diagnostic Mode:

To enter diagnostic mode, proceed as follows:

Turn ignition "ON."
TURN THE HEATER ON FULL COLD (60 DEGREES) AND THE FAN ON FULL HIGH SO THAT COLD AIR IS BLOWING AT ITS MAXIMUM.
Depress the "OFF" and "WARMER" buttons on the Climate Control Center (CCC) simultaneously and hold until the segment check appears on the Instrument Panel Cluster (IPC).

TROUBLE CODE DISPLAY:

After entering On-Board Diagnostics, a segment check is automatically performed and then any trouble code stored in computer memory will be displayed. Codes may be stored for the Powertrain Control Module (PCM), Instrument Panel Cluster (IPC), Air Conditioning Programmer (ACP), Supplemental Inflatable Restraint (SIR), Traction Control System (TCS) or Road Sensing Suspension (RSS) systems.



SELECTING THE SYSTEM:SELECT ACP

After trouble codes have been displayed, a specific vehicle system PCM, IPC, ACP, SIR, TCS, RSS may be selected for testing.

The first available system will be automatically displayed (i.e. PCM?). While selecting the system to test, any of the following actions may be taken:

Depressing the "HI" button on the CCC will select the displayed system for testing.
Depressing the "LO" button on the CCC will display the next available system selection. This allows the display to be stepped through all system choices. This list of systems can be repeated following the end of the system list.
Depressing the "OFF" button the CCC will stop the system selection process and return the display to the beginning of the trouble code sequence.
Select ACP.

SELECTING THE TEST TYPE: SELECT OVERRIDE ACP CODES

Having selected a system, the first available test type will be displayed (i.e. ACP DATA?, ACP CLEAR CODES?, ACP OVERRIDE?). While selecting a specific test type, any of the following actions may be taken:

Depressing the "HI" button on the CCC will select the displayed test type. At this point the first of several specific tests will appear.
Depressing the "LO" button on the CCC will display the next available test type for the selected system. This allows the display to be stepped through all available test type choices. This list of test types can be repeated following the display of the last test type.
Depressing the "OFF" button on the CCC will stop the test type selection process and return the display to the next available system selection.
Select Override ACP Codes , ACP OVERRIDE, or Override - whatever override it displays.
OVERRIDE THE CODES USING THE HOTTER (RED) AND COLDER (BLUE) BUTTONS:
The first code you see is AS00 – leave it alone and advance to the next override by depressing the "LO" button on the CCC.
Go to AS01 – change the value to 01 using the blue and red buttons if it is not already at 01 then advance to the next override by depressing the "LO" button on the CCC.
Go to AS12 – change the value from 84 to 01 and begin driving your car with warm or hot air coming out of the center vents WHEN THE CAR IS IN MOTION and it is warmed up.
Enjoy the heat without going through diagnostic hell (and they say it couldn’t be done since Cadillacs do not provide heat from the center vents - they do).
PS:

AS13 changes flap combinations but doesn’t give any more heat

AS16 changes blower motor speed but doesn’t provide more heat

AS19 doesn’t really do much of anything

AS20 cycles the flaps in through all the AS13 combinations if you change the value to 99 but still no more heat



Changing anything out of sequence resets everything up and you do not get heat.



Again, no fixing vacuum leaks, servos, or controllers – just heat through the center vents – somewhere where it is not supposed to come out of but when your toes are frozen, do you care?



Please share and post this information – my pleasure. My worry is that no one was able to crack these code overrides except for me. Why?



Dr. VH Pashtenko (not an automotive technician, just a person with cold toes who was tired of hearing every excuse why this couldn't be fixed).
Read more at http://www.cadillacforums.com/forum...lle-1985-2005-including-1985/190999-help-no-heat-dash-vents.html?ktrack=kcplink

 

Holy hell Imma have to go try that sometime, I know there are hidden codes when I first went into the diagnostic mode and saw things like option A, B and C and Override and among other strange settings.

So if I do this wrong I won't get ANY heat at all?? How about A/C, because in the summer my AC programmer is bad and I get AC only in the window defrost vent(and I think the floor vents).



Are there other settings to override things such as air/fuel ratio, traction control and speed limiter? Where are these code information located, maybe in the official service manual(the 3-book ones)? I remember taking apart my PCM and saw a removable chip inside... I think it had some switches on it, not sure. Seems like there are things on these cars that can be changed but GM doesn't want us to know how to For instance the speed limiter... it 's gotta to be simple to change it.

 

I do not believe that the OBDII cars have the override function. That went away with OBDI.

 

I see, I just don't want to go in and mess something up and make it worse.




So where did people find info on these "options" that obviously weren't supposed to be accessible by a normal car owner?

 

Not sure where they found that info. Probably in a FSM.

 

Great post from Freakzilla...but I have a question. I followed your directions to a "T". First, how do I save the changes because whenever I go back into the CCC none of my values stayed the same. Second, how long while driving before the heat will blow warm/hot out of the front vents? When I made the changes it
blows cold out of the front vents. 36 degrees here in Texas today and I would like heat blowing out of the front vent not just the defrost vents and floor. Lastly, is this just a tweak or the way the vehicle was designed? I read in a another thread that the 94 Deville was designed to only have heat blow from the top vents/defrost and floor. Is that true?

Thanks in advance

 

----------------------------------
how do I save the changes
because whenever I go back into the CCC
none of my values stayed the same.
you can't -
the "override" is temporary - for testing purposes -
once you are out of the TEST-MODE -
everything goes back to "normal" -

36 degrees here in Texas today
and I would like heat blowing out of the front vent
not just the defrost vents and floor.
you have no control of WHERE the air blows from -
EXCEPT defrost -

heat ONLY comes from the floor and defrost -

ambient and cooled air ONLY comes from the dash vents -

is this just a tweak or the way the vehicle was designed?
it's how the system was designed -

the MODE feature didn't come 'til years later -

 

And do answer the four year old Concours question, they have the same exact controls as Deville. Concours was trim, engine and suspension changes.

 

Thanks basscatt for the confirmation. I also talked to a very good mechanic back in Phoenix at the Cadishop, who's worked on Cadis for over 30 years and also said the same thing. Its a stupid design but it is what it is. Nevertheless, its good to know that I can put the repair money towards something else now.