HVAC BLOWER FAN RUNS CONTINUOUSLY WITH IGN. OFF. GMC Truck Jimmy

SUBJECT: HVAC BLOWER FAN RUNS CONTINUOUSLY WITH IGNITION OFF (REPLACE A/C CONTROL ASSEMBLY)

MODELS: 1998 CHEVROLET AND GMC S/T MODELS 1998 OLDSMOBILE BRAVADA WITH RPO C68

CONDITION:

SOME OWNERS MAY COMMENT THAT THE BLOWER FAN KEEPS RUNNING AFTER THE IGNITION IS TURNED OFF.

CAUSE:

IF THE IGNITION KEY IS TURNED OFF WITHIN A VERY QUICK TIME WINDOW, THE BLOWER SPEED OUTPUT TIMER MAY NOT RESET DURING THE POWER DOWN SEQUENCE. WHEN THIS OCCURS, THE CONTROL ASSEMBLY WILL CONTINUE TO OUTPUT A 8HZ SIGNAL TO THE PULSE WIDTH MODULATION (PWM) BLOWER DRIVER.

THE PWM BLOWER DRIVER IS DESIGNED TO OPERATE AT BETWEEN 30-50HZ, BUT MAY OPERATE AT A FREQUENCY AS LOW AS 8HZ. IF THE KEY IS TURNED OFF DURING THIS VERY QUICK TIME WINDOW, AND A SIGNAL OF 8HZ IS TRIGGERED, THE FAN WILL RUN UNTIL THE BATTERY IS DEAD OR UNTIL THE IGNITION KEY IS CYCLED ON AND OFF.

CORRECTION:

REPLACE THE A/C CONTROL ASSEMBLY USING THE PART NUMBER(S) LISTED BELOW. USE THE SERVICE PROCEDURE IN SECTION 1B OF THE SERVICE MANUAL.

PARTS INFORMATION:

P/N DESCRIPTION APPLICATION QTY

9356175 CONTROL ASM., HTR + A/C RPO'S X88, Z88 + ZM8 1 (W/ R/WDO DEFOG SW) (EXCEPT Z49)

9356185 CONTROL ASM., HTR + A/C RPO Z70 (EXCEPT Z49) 1 (W/ R/WDO DEFOR SW)

9356195 CONTROL ASM., HTR + A/C RPO'S Z49, VD1 + VE1 1 (W/ R/WDO DEFOG SW)

PARTS ARE EXPECTED TO BE AVAILABLE 5-18-98 FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION DESCRIPTION LABOR TIME

D0362 CONTROL ASSEMBLY USE PUBLISHED (A/C) - REPLACE LABOR OPERATION TIME

IMPORTANT: LABOR OPERATION IS CODED TO BASE VEHICLE COVERAGE IN THE WARRANTY SYSTEM.

FIGURES: 00 ATTACHMENTS: 00

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.