You Want Heat in Your DeVille Now? Here's how with the push of a few buttons

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):
:banghead:
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. :screwy:
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).

How is blowing heat out the dash vents gonna warm up your toes? would you want it blowing out the floor vents.

How is blowing heat out the dash vents gonna warm up your toes? would you want it blowing out the floor vents.
It won't but it will at least heat the car enough until you get some heat in it and that will warm your toes eventually on a long trip. On a short trip, it's a fast way a pre-heating the car (AS01 set at 45 and AS 12 set at 17 works best for pre-heating).

Either way, it will also allow you to get some heat into an ice-cold car when nothing else works such as when your thermostat is stuck open (as mine is) or to check to see if your heater core is plugged (to avoid unnecessary core repair).

Eventually, in freezing condition, it will blow air at about 48 - 52 degrees but, when you're freesing, this is better than no heat at all.

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

:icon16:

Good info to keep on hand! Thanks.