AIR COMING FROM I/P VENT WHILE IN HEATER MODES OR A DELAY. Buick Skylark 1997

SUBJECT: AIR COMING FROM I/P VENT WHILE IN HEATER MODES OR A DELAY OCCURS WHEN CHANGING TO A NEW MODE SETTING (DIAGNOSE/MODIFY/ REPLACE)

MODELS: 1996-97 BUICK SKYLARK 1996-97 OLDSMOBILE ACHIEVA 1996-97 PONTIAC GRAND AM

CONDITION:

SOME OWNERS MAY COMMENT ON ONE OF THE FOLLOWING CONDITIONS:

CONDITION A:

AIR IS FELT COMING THROUGH THE I/P VENTS WHILE THE HVAC SYSTEM IS IN "HEATER" MODES. NO AIR SHOULD BE FELT THROUGH THE I/P VENTS IN "HEATER" MODES.

CONDITION B:

A DELAY OCCURS WHEN CHANGING TO A NEW MODE SETTING. THE MODE TYPICALLY CHANGES WITHIN 1 MINUTE AND IS ACCOMPANIED BY A HISSING SOUND.

CAUSE:

CONDITION A:

THE MODE DOOR MAY NOT SEAL TIGHTLY TO THE HVAC MODULE, ALLOWING AIR TO ESCAPE THROUGH THE I/P VENTS.

CONDITION B:

THE MODE SWITCH/VALVE ASSEMBLY MAY NOT IMMEDIATELY DISTRIBUTE VACUUM TO THE APPROPRIATE HVAC MODULE VACUUM ACTUATORS.

CORRECTION:

DIAGNOSE THE SYSTEM TO DETERMINE THE CONDITION -

DOES AIR COME OUT THE I/P VENTS IN ALL "HEATER" MODES (HEAT, BLEND, DEFROST) BUT RESPONDS CORRECTLY IN ALL OTHER MODES? IF "YES", GO TO DIAGNOSIS FOR CONDITION A (MODE DOOR CHECK). IF "NO", GO TO DIAGNOSIS FOR CONDITION B (CONTROL ASSEMBLY CHECK).

CONDITION A:

DIAGNOSE -

MODE DOOR CHECK:

1. REMOVE I/P COMPARTMENT. REFER TO SECTION 8C2 IN THE SERVICE MANUAL. VERIFY VACUUM AT THE MODE ACTUATOR (YELLOW LABEL) RED HOSE AND OBSERVE DOOR LINKAGE MOVEMENT. MAKE CORRECTIONS IF NECESSARY AND RECHECK. IF CONDITION WAS FOUND, CORRECTED, AND AIR NOW COMES OUT OF THE CORRECT DUCTS BASED ON THE MODE SETTING, REINSTALL THE I/P COMPARTMENT AND STOP. IF VACUUM AND DOOR MOVEMENT ARE VERIFIED AND THE AIR STILL COMES OUT OF THE I/P VENTS IN ALL "HEATER" MODES, PERFORM THE SERVICE PROCEDURE LISTED BELOW THEN STOP - DO NOT PERFORM DIAGNOSIS FOR CONDITION B.

SERVICE PROCEDURE:

MODIFY MODE DOOR ACTUATOR LINKAGE. 1. REMOVE VACUUM LINES FROM MODE DOOR ACTUATOR. 2. REMOVE RETAINING CLIP AT END OF ACTUATOR SHAFT. 3. REMOVE ACTUATOR FROM HVAC MODULE. 4. DRILL 5/32 IN. HOLE, 5 MM UP THE ACTUATOR LINK (CLOSER TO THE ACTUATOR HOUSING). 5. INSTALL ACTUATOR TO HVAC MODULE. 6. INSTALL MODE DOOR SHAFT TO NEW HOLE ON ACTUATOR LINK WITH RETAINING CLIP. 7. INSTALL VACUUM LINES TO ACTUATOR.

VERIFY THAT THERE IS NO AIR COMING THROUGH THE I/P VENTS IN "HEATER" MODES WITH BLOWER ON "HIGH". IF LEAKAGE IS STILL PRESENT THROUGH I/P VENTS, THEN DIAGNOSE HVAC MODULE. REFER TO SECTION 1B IN APPLICABLE SERVICE MANUAL.

CONDITION B:

VIN BREAKPOINTS:

BEGINNING ENDING WITH REGULAR PRODUCTION MODEL VEHICLE DATE CONTROL ASSEMBLY OPTION CODE ===== ============ ================ ==================

BUICK 1996 SOP FEB. 22, 1996 C60 (P/N 16221014)

OLDSMOBILE 1996 SOP FEB. 22, 1996 C60 (P/N 16173373)

PONTIAC 1996 SOP FEB. 22, 1996 C60 (P/N 16173502)

1996 SOP FEB. 28, 1996 C41 (P/N 16173512)

1996 SOP FEB. 26, 1996 C60 (P/N 16173362)

1996 SOP MARCH 5, 1996 C41 (P/N 16173372)

DIAGNOSE -

CONTROL ASSEMBLY CHECK:

WHILE OPERATING THE HVAC SYSTEM, A DELAY OCCURS WHEN CHANGING TO A NEW MODE SETTING. THE MODE CHANGE IS TYPICALLY ACCOMPANIED BY A HISSING SOUND. THIS COULD OCCUR IN ANY ONE OR MORE MODES. IT COULD BE AN INTERMITTENT EVENT (POSSIBLY SUBJECT TO AMBIENT TEMPERATURES GENERALLY BELOW 35 DEGREES FAHRENHEIT (1 DEGREE CELSIUS). THEREFORE, THE CONTROL ASSEMBLY COULD OPERATE CORRECTLY WHEN IT IS CHECKED.

1. DOES AIR COME OUT THE CORRECT DUCTS BASED ON THE MODE SETTING? IF "YES", PERFORM THE SERVICE PROCEDURE LISTED BELOW. IF "NO", GO TO STEP 2.

2. REMOVE I/P COMPARTMENT. REFER TO SECTION 8C2 IN THE SERVICE MANUAL. VERIFY VACUUM AT THE SOURCE (PURPLE HOSE) AND AT THE VACUUM ACTUATORS. VERIFY MODE AND DEFROST DOOR OPERATION. MAKE CORRECTIONS IF NECESSARY. IF CONDITION WAS FOUND, CORRECTED, AND AIR NOW COMES OUT OF THE CORRECT DUCTS BASED ON THE MODE SETTING, REINSTALL THE I/P COMPARTMENT AND STOP. IF NOT, PERFORM THE SERVICE PROCEDURE LISTED BELOW, THEN STOP. DO NOT PERFORM THE DIAGNOSIS FOR CONDITION A.

SERVICE PROCEDURE -

REPLACE THE MODE SWITCH/VALVE ASSEMBLY.

1. REMOVE THE CONTROL ASSEMBLY FROM THE VEHICLE. REFER TO SECTION 1B OF THE APPLICABLE SERVICE MANUAL. 2. REMOVE THE MODE SWITCH/VALVE ASSEMBLY FROM THE CONTROL ASSEMBLY (SEE FIGURE 1). 3. INSTALL THE MODE SWITCH/VALVE ASSEMBLY TO THE CONTROL ASSEMBLY, SEE PART NUMBERS LISTED BELOW. VERIFY THAT THE SCREWS ARE FULLY SEATED AND NOT STRIPPED. 4. INSTALL CONTROL ASSEMBLY TO VEHICLE. 5. VERIFY CORRECT AIR DISTRIBUTION. 6. COMPLETE INSTALLATION.

PARTS INFORMATION:

P/N 16248149 (FOR VEHICLES EQUIPPED WITHOUT A/C, RPO C41) P/N 16248139 (FOR VEHICLES EQUIPPED WITH A/C, RPO C60)

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION NUMBER DESCRIPTION LABOR TIME =============== =========== ==========

CONDITION A:

D1787 UPPER/LOWER MODE ACTUATOR, USE PUBLISHED VACUUM DIAPHRAGM - R + R LABOR TIME

CONDITION B:

D0160 VALVE, CONTROL ASSEMBLY USE PUBLISHED VACUUM SELECTOR - REPLACE LABOR TIME

FIGURES: 01 ATTACHMENTS: 00

FIGURE 1: 1. MODE SWITCH/VALVE ASSEMBLY 2. CONTROL ASSEMBLY

Object Number: 96801 Size: FS

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.