For 1990-2009 cars

# INFO. ON A/C COMPRESSOR 'BRAP' NOISE DURING HARD ACCEL.

#### SUBJECT: INFORMATION ON A/C COMPRESSOR "BRAP" NOISE DURING HARD ACCELERATION

#### MODELS: 1994 BUICK SKYLARK 1994 CHEVROLET CORSICA AND BERETTA 1994 OLDSMOBILE ACHIEVA 1994 PONTIAC GRAND AM

ENGINE APPLICATIONS: VIN A - (RPO LG0) VIN D - (RPO LD2) VIN 3 - (RPO L40) VIN 4 - (RPO LN2)

SOME OWNERS MAY EXPRESS CONCERN WITH AN A/C COMPRESSOR "BRAP" NOISE. THIS NOISE MAY OCCUR UNDER THE FOLLOWING CONDITIONS:

1. VIN A, D, 3 AND 4 ENGINES ON WIDE OPEN THROTTLE ACCELERATION UNDER HIGH A/C COMPRESSOR HEAD PRESSURE.

2. VIN A, D AND 3 ENGINES ON KEY-UP ONCE THE ENGINE HAS SIMULTANEOUSLY EXCEEDED 2,000 RPM, 20 PERCENT TPS AND VEHICLE MOVING 20 MPH.

3. VIN A ENGINES WITH MANUAL TRANSMISSION WHEN A SUDDEN ENGINE RPM DROP FROM ABOVE 6,400 ENGINE RPM TO BELOW 4,200 ENGINE RPM OCCURS.

THE A/C COMPRESSOR IS CALIBRATED TO DISENGAGE UNDER ANY ONE OF THESE CONDITIONS. UPON REENGAGEMENT OF THE COMPRESSOR CLUTCH, ABOVE 3,800 ENGINE RPM, A "BRAP" NOISE MAY BE CREATED BY THE WOBBLE PLATE REGAINING SPEED AND REINSTATING NORMAL A/C SYSTEM PRESSURES.

UNDER THE ABOVE CONDITIONS, A COMPRESSOR "BRAP" NOISE IS CONSIDERED TO BE NORMAL.

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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 1993 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.