For 1990-2009 cars

# INFO. ON PROCEDURES TO ASSIST IN DIAGNOSIS OF A/C

#### SUBJECT: INFORMATION ON PROCEDURES TO ASSIST IN DIAGNOSIS OF A/C "TYPE" NOISES (MOAN, GROWL)

#### MODELS: 1996 BUICK LESABRE, PARK AVENUE RIVIERA 1996 OLDSMOBILE EIGHTY EIGHT, LSS, NINETY EIGHT 1996 PONTIAC BONNEVILLE WITH 3800 ENGINE (VINS K, 1 - RPOS L36, L67)

TO ASSIST IN THE DIAGNOSIS OF A/C COMPRESSOR "TYPE" NOISES, (MOAN, GROWL), THE FOLLOWING PROCEDURES SHOULD BE FOLLOWED PRIOR TO REPLACING THE A/C COMPRESSOR RELATED TO A NOISE CONDITION.

A/C COMPRESSOR MOAN NOISE: THIS CONDITION IS NOTICED BETWEEN IDLE AND 800 RPM DURING A/C COMPRESSOR OPERATION. THE CAUSE OF AN A/C COMPRESSOR MOAN NOISE CAN BE BROKEN DOWN INTO FOUR AREAS:

1. AN A/C COMPRESSOR MOAN NOISE CAN BE CAUSED IF THE A/C LINES ARE GROUNDED TO THE VEHICLE. COMMON GROUND POINTS ARE THE LIQUID LINE CONTACTING THE STRUT TOWER OR THE COMPRESSOR DISCHARGE LINE CONTACTING THE RADIATOR. INSPECT ALL A/C LINE ROUTINGS TO ENSURE THAT THEY ARE PROPERLY ROUTED.

2. VIBRATION OF THE GENERATOR DURING A/C OPERATION CAN BE CAUSED BY THE GENERATOR SUPPORT BOLTS LOOSE OR IMPROPERLY POSITIONED. VERIFY CORRECT TORQUE BY LOOSENING AND THEN RETORQUING GENERATOR BOLTS IN THE FOLLOWING SEQUENCE:

A. RETORQUE FRONT GENERATOR BOLT AND GENERATOR BRACE BRACKET TO 50 N.M (37 LB FT). B. RETORQUE REMAINING GENERATOR BRACE BRACKET BOLTS TO 30 N.M (22 LB FT). C. RETORQUE TOP "L" SHAPED GENERATOR BRACE TO 30 N.M (22 LB FT). D. RETORQUE LOWER "L" SHAPED GENERATOR BRACE TO 25 N.M (18 LB FT).

3. THE COMPRESSOR BRACKET TO ENGINE MOUNTING BOLTS MAY BE LOOSE. IF LOOSE, REMOVE BOLTS AND REPLACE WITH P/N 25624806. THESE BOLTS ARE LONGER THAN THE ORIGINAL BOLTS. NEW BOLTS ARE TORQUED TO 100 N.M (74 LB FT).

#### IMPORTANT: IT IS POSSIBLE TO REMOVE THE COMPRESSOR FROM THE BRACKET WITHOUT DISCHARGING THE SYSTEM.

4. A/C COMPRESSOR GROWL NOISE: THIS CONDITION IS NOTICED THROUGHOUT THE ENGINE OPERATING RPM RANGE DURING A/C OPERATION.

A. A LOW REFRIGERANT CHARGE WILL CAUSE A GROWL CONDITION. USE A J-39400, ELECTRONIC LEAK DETECTOR, OR R134A REFRIGERANT DYE TO LOCATE THE LEAK. IF A LEAK IS LOCATED, USE THE APPROPRIATE LABOR OPERATION FROM THE LABOR TIME GUIDE FOR THIS REPAIR. RECHARGE SYSTEM TO 2 POUNDS AND RECHECK FOR LEAKS.

B. IF NO REFRIGERANT LEAK IS FOUND, THEN VERIFICATION OF LOW REFRIGERANT REQUIRES RECOVERY OF THE REFRIGERANT CHARGE. COMPARE THE RECOVERED CHARGED WEIGHT AGAINST SPECIFICATIONS. A RECOVERED CHARGE UNDER 1.75 OF A POUND INDICATES A LOW CHARGE. RECHARGE SYSTEM TO 2 POUNDS AND CHECK FOR LEAKS.

#### PARTS INFORMATION:

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

#### WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

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

D4237 STEPS 1, 2, 3: 0.3 HR BRACKET, COMPRESSOR MOUNTING R/R OR REPLACE (ALL)

ADD: STEPS 1, 2, 3: 0.8 HR TO REPLACE COMPRESSOR BRACKET TO ENGINE MOUNTING BOLTS

USE APPROPRIATE STEP 4-A USE PUBLISHED LABOR OP FROM LABOR TIME LABOR TIME GUIDE

T2040 STEP 4-B: 0.7 HR RECOVER/RECHARGE A/C 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.

COPYRIGHT 1996 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.