HVAC DUCT TEMP/AIR FLOW CONCERNS/COOL AIR FROM DEFROST

REVISION: 09/25/95

THIS BULLETIN IS BEING REVISED TO CORRECT WARRANTY INFORMATION FOR THE TAS/CAMS SYSTEM ONLY. CORRECT INFORMATION WAS PROVIDED IN THE PRINTED PAPER BULLETIN. ********************************************************************

REVISION: 10/02/95

THIS BULLETIN IS BEING REVISED TO INFORM "GM OF CANADA" AND "NAES" DEALERS THAT THEY ARE NOT AUTHORIZED TO UTILIZE THIS SERVICE BULLETIN. ********************************************************************

SUBJECT: HVAC DUCT TEMP AND/OR AIR FLOW CONCERNS/COOL AIR FROM DEFROST (MULTIPLE REPAIR PROCEDURES)

MODELS: 1991-92 CADILLAC DEVILLES AND FLEETWOODS

"GM OF CANADA" AND "NAES" DEALERS ARE NOT AUTHORIZED TO UTILIZE THIS SERVICE BULLETIN.

THIS BULLETIN INCLUDES NEW PARTS AND ADDITIONAL DIAGNOSTIC INFORMATION FOR SIDE-TO-SIDE AND/OR UP-TO-DOWN TEMP VARIATION. FOR IMBALANCED DEFROSTER OPERATION ON DRIVER'S SIDE SEE BULLETIN T-92-14 (CORPORATE BULLETIN NUMBER 101204). FOR CONDENSATE DRIPPING FROM THE HEATER DUCTS SEE T-91-89 (CORPORATE BULLETIN NUMBER 101101). FOR WHISTLING NOISE FROM HVAC TEMPERATURE DOOR A REVISED BULLETIN WILL BE ISSUED IN THE NEAR FUTURE.

SOME VEHICLE CLIMATE CONTROL SYSTEMS MAY EXHIBIT COOL AIR FROM THE DEFROST AND SIDE WINDOW DEFOG OUTLETS AND/OR IMBALANCED DUCT TEMPERATURES FROM LEFT TO RIGHT WHEN OPERATING IN "AUTO" SETTINGS WHICH CALL FOR HEAT OR FOR DEFOG MODE. THIS CONDITION MAY BE DESCRIBED AS CAUSING COLD HANDS, COLD FACE, AND/OR COLD LEFT KNEE, OR WARM DRIVER AND COOL PASSENGER AND IS MOST LIKELY TO OCCUR AFTER A 40 TO 45 MINUTE DRIVE AS THE INTERIOR VEHICLE TEMPERATURES BEGIN TO REACH THE DESIRED SETTING AND THE SYSTEM BEGINS TO STABILIZE.

AS THE ECC SYSTEM BEGINS TO STABILIZE WHILE IN THE HEAT MODE, THE TEMPERATURE OF THE HEATED AIR DELIVERED TO THE DUCTS BEGINS TO LOWER TO HELP MAINTAIN THE REQUESTED INTERIOR TEMPERATURE. THE SYSTEM USES MANY HARDWARE AND SOFTWARE COMPONENTS TO MIX AND DELIVER THE AIR TO THE PROPER DUCTS TO MAINTAIN COMFORT. THE FOLLOWING COMPONENTS MAY CONTRIBUTE TO THE CAUSE OF THIS CONDITION:

A. INSIDE AIR TEMP SENSOR - MAY NOT BE SEATED AND/OR SEALED PROPERLY ALLOWING HEATED AIR FROM THE I/P INTERIOR TO BE DRAWN INTO THE SENSOR PRODUCING A FALSE SENSOR READING.

B. ASPIRATOR HOSE AND ASPIRATOR - HOSE MAY BE KINKED OR DAMAGED OR ASPIRATOR MAY NOT BE PROPERLY SEATED TO MODULE PREVENTING THE NECESSARY AIR FLOW FROM THE INTERIOR OVER THE SENSOR.

C. AIR MIX VALVE/DOOR - MAY BE MISADJUSTED PREVENTING THE PROPER MIX OF HEATED AND COOLED AIR FROM ENTERING THE DUCTS. (REFER TO SECTION 1B OF THE SERVICE INFORMATION MANUAL FOR PROPER AIR MIX VALVE ADJUSTMENT.)

IMPORTANT: IT IS NECESSARY TO INSPECT EACH OF THESE ITEMS TO ASSURE A COMPLETE AND SATISFACTORY CORRECTION.

IF AFTER INSPECTION OF THE ABOVE ITEMS NO PROBLEM IS FOUND, THEN THE PROBLEM MAY BE CAUSED BY THE IMPROPER MIXING OF THE AIR BY THE BAFFLES CONTAINED IN THE HVAC MODULE. TO CORRECT THIS CONDITION REPLACE: A. SPLITTER WALL P/N 52461742 B. UPPER MIX DOOR BAFFLE P/N 52456147 C. LOWER MIX DOOR BAFFLE P/N 52456146 D. PUSH-ON WASHER P/N 9428633 E. 1991 BCM PROM P/N 16183894 (1991) 1992 BCM PROM P/N 16183880 (1992)

PARTS ARE EXPECTED TO BE AVAILABLE ON SEPTEMBER 14, 1992. IN CASE OF LIMITED INVENTORY, PARTS WILL BE PLACED ON 400 CONTROL TO WAIVE VIP SURCHARGES. ONLY VERIFIABLE EMERGENCY VIP ORDERS WILL BE ACCEPTED. SPO WILL MAKE EVERY EFFORT TO OBTAIN PARTS. HOWEVER, THE PART WILL BE SHIPPED PREMIUM TRANSPORTATION AT DEALER'S EXPENSE, AND ALL OTHER ORDER TYPES WILL BE PLACED ON BACK ORDER UNTIL THE 400 CONTROL IS REMOVED.

THESE PROM'S CONTAINED ENHANCED CONTROL CALIBRATIONS WHICH ARE SPECIFICALLY DESIGNED TO COORDINATE WITH THE NEW BAFFLES AND SPLITTER.

IMPORTANT: IF 1992 MODEL AND VIN SEQUENCE ARE AFTER BREAKPOINT N4257163 OR IF 1991-1992 MODELS HAVE HAD BULLETIN T-92-30 (CORPORATE BULLETIN NUMBER 111101R) PERFORMED PREVIOUSLY (ON-BOARD DIAGNOSTIC PARAMETER -31 WOULD BE 59 FOR 1991 AND 67 FOR 1992), THEN THERE IS NO NEED TO REPLACE SPLITTER WALL OR AIR MIX DOOR BAFFLES. IN THIS CASE ONLY, JUST REPLACE BCM PROM AS INDICATED IN STEP 26 OF THIS BULLETIN. FOR WARRANTY PURPOSES USE LABOR OPERATION N4801 FOR .6 HOUR WHEN REPLACING PROM ONLY.

NOTICE: TO PREVENT SHORT CIRCUIT DAMAGE WHEN REMOVING OR INSTALLING CERTAIN ELECTRICAL UNITS, DISCONNECT THE NEGATIVE (-) BATTERY CABLE AND TURN IGNITION SWITCH TO "OFF" POSITION.

CAUTION:

THE PROCEDURE THAT FOLLOWS MUST BE FOLLOWED IN THE ORDER LISTED TO TEMPORARILY DISABLE THE SUPPLEMENTAL INFLATABLE RESTRAINT (SIR) SYSTEM AND PREVENT FALSE DIAGNOSTIC CODES FROM SETTING. FAILURE TO FOLLOW PROCEDURES COULD RESULT IN POSSIBLE AIR BAG DEPLOYMENT, PERSONAL INJURY, OR OTHERWISE UNNEEDED SIR SYSTEM REPAIRS.

NOTICE: THE DERM CAN MAINTAIN SUFFICIENT VOLTAGE TO CAUSE A DEPLOYMENT FOR UP TO TEN MINUTES AFTER THE IGNITION SWITCH IS TURNED OFF OR BATTERY IS DISCONNECTED.

DISABLE SIR SYSTEM:

1. REMOVE SIR FUSE 18 FROM FUSE PANEL.

2. REMOVE RIGHT AND LEFT SOUND INSULATORS.

3. REMOVE CONNECTOR POSITION ASSURANCE (CPA) AND YELLOW TWO-WAY SIR HARNESS CONNECTOR AT BASE OF STEERING COLUMN.

REMOVE I/P UPPER TRIM PANEL:

4. REMOVE A/C OUTLET DEFLECTORS AND SCREWS FOUND BEHIND EACH.

5. REMOVE THREE SCREWS THROUGH DEFROSTER GRILL.

6. DISCONNECT CONNECTOR FOR INSIDE AIR TEMP SENSOR AND ASPIRATOR TUBE.

7. DISCONNECT SOLAR SENSOR FROM TRIM PAD AND REMOVE UPPER TRIM PANEL.

REMOVE LOWER STEERING COLUMN OPENING FILLER AND REINFORCEMENT PLATE:

8. SNAP OUT UPPER STEERING COLUMN FILLER AND REMOVE SCREWS HOLDING FILLER AND REINFORCEMENT PLATE.

9. LOWER STEERING COLUMN TO REST ON FRONT SEAT.

REMOVE LOWER I/P TRIM PAD:

IMPORTANT: BE SURE TO REPLACE, NOT REPAIR, FILLER TRIM AND/OR BRACKET IF ANY DAMAGE TO EITHER PART IS EVIDENT.

10. REMOVE TWO SCREWS AND THE LOWER TRIM PAD SUPPORT.

11. REMOVE THE NUT FROM ACCELERATOR PEDAL STUD AND THE SCREW FROM I/P END OF I/P LOWER BRACE AND REMOVE BRACE.

12. REMOVE REMAINING RETAINING SCREW AND REMOVE LOWER TRIM PAD ASSEMBLY FROM VEHICLE - TWO PEOPLE REQUIRED.

REMOVE A/C DISTRIBUTOR (REFER TO FIGURE 1):

13. DISCONNECT VACUUM HOSE FROM VACUUM ACTUATORS.

14. REMOVE VACUUM HARNESS RETAINERS FROM AIR DISTRIBUTOR ASSEMBLY AND POSITION VACUUM HARNESS ASIDE.

15. REMOVE SIDE WINDOW DEFOGGER HOSE/OUTLET FROM AIR DISTRIBUTOR ASSEMBLY.

16. REMOVE SCREWS FROM FLOOR AIR OUTLET.

17. REMOVE SCREWS AND NUT ATTACHING AIR DISTRIBUTOR TO FRONT OF DASH AND REMOVE ASSEMBLY.

REMOVE SPLITTER WALL AND AIR MIX DOOR BAFFLES:

18A. FOR 1991 VEHICLES PRIOR TO VIN SEQUENCE 304903, REMOVE SEPARATOR SCREW AND REMOVE AND DISCARD SPLITTER. REFER TO FIGURE 1, VIEW A.

18B. FOR 1992 AND 1991 VEHICLES AFTER VIN SEQUENCE 304903, APPLY A FIRM AND STEADY DOWNWARD PRESSURE TO SPLITTER WALL TO DISRUPT THE WELD. (PREHEATING WELD SEAMS WITH A HEAT GUN PRIOR TO APPLYING PRESSURE WILL ASSURE A CLEANER BREAK.) REMOVE AND DISCARD SPLITTER. REFER TO FIGURE 1, VIEW A.

19. SOME EARLY 1991 VEHICLES MAY NEED MODIFICATION TO THE NOTCH SHOWN IN FIGURE 2. IF SO, WITH A HOT KNIFE OR HACKSAW, EXTEND THE NOTCH ON THE HEATER/EVAPORATOR MODULE TO ACCOMMODATE THE ADDITIONAL RETENTION TAB. REFER TO FIGURE 2.

20. PHOTOCOPY TEMPLATE PROVIDED IN FIGURE 3 AND MODIFY P/N 52461742 TO MATCH TEMPLATE.

21. REMOVE PROGRAMMER, HEATER CORE ACCESS DOOR, AND TWO SCREWS HOLDING CORE IN PLACE.

22. USING A 11/64" DRILL BIT, DRILL OUT TEMPERATURE BAFFLE HEAT STAKES IN THE TEMPERATURE VALVE (AIR MIX DOOR) THROUGH THE ACCESS PROVIDED BY THE REMOVAL OF THE SPLITTER WALL. REFER TO FIGURES 2 AND 4.

INSTALL NEW SPLITTER WALL AND BAFFLES:

23. INSTALL NEW BAFFLES - LOWER BAFFLE, P/N 52456146, AND UPPER BAFFLE, P/N 52456147. SECURE TIGHTLY IN PLACE WITH PUSH-ON RETAINER WASHER, P/N 9428633, USING THE ACCESS PROVIDED BY MOVING THE HEATER CORE SLIGHTLY TO THE SIDE.

24. APPLY A BEAD OF DOW CORNING #111 SILICONE GREASE, OR EQUIVALENT, TO THE SEAMS WHERE THE BAFFLES ARE ATTACHED TO THE TEMPERATURE VALVE (AIR MIX DOOR) AS SHOWN IN FIGURE 5, VIEW A.

25. INSTALL MODIFIED SPLITTER WALL BY DRILLING ONE HOLE AND RIVETING THE WALL AS SHOWN IN VIEW A OF FIGURE 1.

26. REPLACE BCM PROM IN ACCORDANCE WITH THE CHART BELOW:

MODEL PROM BROADCAST YEAR I.D. CODE P/N

1991 50 BCSL 16183894 1992 68 BCRS 16183880

27. REASSEMBLE AIR DISTRIBUTOR AND I/P.

28. ENABLE SIR, CONNECT BATTERY (-), AND PERFORM IDLE LEARN.

FOR WARRANTY PURPOSES USE LABOR OPERATION T6569 AT 3.1 HOURS WHEN PERFORMING COMPLETE BULLETIN WHICH INCLUDES DISABLE AND ENABLE SIR, TPS, AND IDLE LEARN.

IF VEHICLE REQUIRES ONLY A BCM PROM UPDATE, USE LABOR OPERATION N4801 AT .6 HOUR.

FIGURES: 5

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.

COPYRIGHT 1995 CADILLAC MOTOR CAR DIVISION, GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.