REDUCTION IN A/C PERFORMANCE (REVISED COMPRESSOR BRACKET)

LOSS OF A/C PERFORMANCE OR EXCESSIVE A/C NOISE (BRACKET INSTALLATION PROCEDURES) REVISED TO CORRECT TEXT IN ACCORDANCE WITH ILLUSTRATION. CHANGE IN PARAGRAPH 3.

VEHICLES AFFECTED: 1987-88 "M" CAR -----------------

Some of the subject vehicles may exhibit excessive noise or loss of performance from the air conditioning system. These conditions may occur as a result of a loss of torque by the A/C compressor mounting bracket fasteners. In extreme circumstances, the loss of torque at one or more of the bracket fasteners may result in a cracked upper or lower bracket. Vehicles exhibiting the above conditions should first be examined to establish if the fasteners are at the correct torque values and that the A/C compressor brackets are not cracked before performing A/C diagnostic procedures.

Reference Figure 1, fasteners identified by numbers 3

(2 places), 6 (2 places 1 -1 shown), 7 (3 places - 2 shown), 9 (1 place) and 10 (1 place) are to be checked for retaining torque. If the torque is less than 15 ft. lbs. (20 Nm), the fastener is to be reinstalled following the appropriate part of the installation procedure that follows:

Both upper and lower compressor mounting brackets are to be visually inspected for cracks and replaced as necessary following the procedures detailed for the installation or reinstallation of the A/C compressor and mounting brackets.

A/C compressor mounting bracket and compressor assembly installation procedures:

NOTICE: FAILURE TO SECURE ALL FASTENERS BY THE FOLLOWING INSTRUCTIONS MAY RESULT IN LOSS OF TENSION ON BOLTS DUE TO INSUFFICIENT TORQUE ON FASTENERS.

Reference Figure 1 for component identification numbers.

1. Install compressor (1) to lower bracket (2) using two (2) bolts 10mm x 1.25mm x 25mm (3) place three (3) drops of Loctite 271 or equivalent on each bolt, and two (2) 10mm wave washers (4). Snug the bolts until the compressor will stay in position but still rotate around bolts.

2. Install lower bracket and compressor on studs previously installed. Finger tighten two (2) nuts 10mm x 1.25mm 0512(6) and wave washers (4) on studs. Install one (1) 8mm x 1.25mm x 20mm bolt (7) and 8mm wave washer (8) through ear of lower bracket into engine.

THE FOLLOWING SEQUENCE MUST BE USED: REFERENCE FIGURE 1 FOR TORQUE SPECIFICATIONS.

First tighten the 8mm bolt (7). Second, tighten two (2) 10mm nuts (6) Final assembly must be done from below vehicle using hand wrenches to assure sufficient torque.

3. Install upper bracket with idler pulley attached (11R) to engine using two (2) 8mm x 1.25mm x 20mm bolts (7) and wave washers (8) and to compressor using one (1) 10mm x 1.25mm x 30mm bolt (10) and wave washer (4). Tighten two (2) 8mm bolts(7) and one 10mm bolt (10).

4. THIS STEP IS VERY IMPORTANT: From below vehicle, tighten two (2) bolts (3) previously snugged through compressor ears (with Loctite), using hand wrenches to assure proper torque.

5a. For Non Turbocharged Vehicles: Install compressor drive belt around crank shaft pulley. Compressor clutch and idler pulley. Adjust belt to proper tension and torque idler pulley shoulder nut to 40 ft. lbs. See Figure 2..

5b. For Turbocharged Vehicles:

Install compressor drive belt around crankshaft and compressor pulleys. Adjust belt tension by positioning compressor, tighten retaining nut to 40 ft. lbs.

Use the most applicable labour operation from the Canadian Labour Time Guide and claim 1.1 hours.

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.