A/C - Diagnosis of Noises (Moan, Growl)
File In Section: 1 - HVACBulletin No.: 63-12-10
Date: May, 1996
INFORMATION
Subject:
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 as shown.