A/C - Compressor Growl Diagnosis & Correction
Bulletin No. T 85-100File in Group 1
Number 24
Corp. Ref. No. 8050408
Date Aug. '85
SUBJECT: AIR CONDITIONING COMPRESSOR GROWL
MODELS AFFECTED: 1985 DEVILLES AND FLEETWOODS EQUIPPED WITH HT4100 ENGINE
Some 1985 FWD Deville and Fleetwood owners may experience a rattle, buzz, growl, whine or moaning noise which is evident only at certain engine speed ranges with the air conditioning (A/C) compressor engaged. This noise may be caused by vibration of the A/C compressor clutch driver, A/C hoses and/or lines and A/C compressor pumping pressure pulses. These pressure pulses are transmitted through the A/C compressor hose assembly, condenser, evaporator and accumulator assemblies. Compressor pulsation noise is more pronounced when operating at maximum cooling demand (high ambient temperatures and humidity). The following procedure should be followed to properly diagnose and correct these conditions.
1. Start car. Set Electronic Climate Control as follows: 60~F AUTO mode, LO fan. Allow car to warm up by idling 3-4 minutes.
2. Enter ECM diagnostics as described on page 1C-16 of the 1985 FWD Deville and Fleetwood Service Information Manual. Enter E.9.0 ECM data display diagnostic parameter P.1.1 (engine RPM).
3. With the transaxle in "Park", observe and record the level and sound of noises when the compressor is engaged ("Outside Temp" status light is displayed on the CCP) at the following engine speeds:
A. 1730 RPM
B. 1650 RPM
C. 1500 RPM
D. 1100 RPM
E. 950 RPM
4. Set the Electronic Climate Control as follows: 60~F ECON mode, LO fan.
5. With the transaxle in "Park", once again observe and record the level and sound of noises at the above listed engine speeds.
If the noise level does NOT decrease when the A/C compressor is off (ECON mode), then the noise is NOT A/C related and the following procedures are not applicable.
If the vehicle is not equipped with damped A/C clutch driver (P/N 2724325) and a metallic-type rattle or buzz is noticed at either 1650 or 1100 RPM, but not at the other engine speeds, please refer to Serviceman Bulletin No. T-84-102, Group 1, Number 17, "Air Conditioning Clutch Driver Noise" for corrective action.
If a growl (low frequency moan) is present, the following procedures should be followed to correct this condition. If the noise level does not decrease after performing the following six steps, then the noise is not A/C compressor growl and cannot be corrected by this bulletin.
1. Perform BCM PROM check and replace as required, per Serviceman Bulletin No. T-85-86, Group 1, Number 23, "Insufficient A/C Cooling at Idle".
2. Isolate the accumulator as follows:
a. Remove accumulator bracket and drill out both existing attachment holes (in the bracket) to 31/64 inch.
b. Install well nuts, P/N 3903539, in the holes (the rubber shoulder of the well nut goes to the bodyside and the threaded portion points toward the accumulator).
c. Reinstall the accumulator bracket using bolts, P/N 3903536. Tighten until the bolt shoulder comes in contact with the threaded portion of the well nut, do not twist the rubber portion.
3. Isolate the liquid line as follows:
a. Remove the non-isolated front liquid line clip (at the high pressure fitting).
b. Install the isolated clip, P/N 1608426 using screw P/N 11504689 (at the high pressure fitting). The accumulator screws not re-used in step 2 above (P/N 11504689) may be used.
c. Remove the liquid line portion of clip at right hand strut tower (only early vehicles have this clip).
d. Remove the liquid line from the plastic clip (located under the accumulator) and relocate upward, so the liquid line and the high side temperature sensor are not contacting the body or the plastic clip.
4. Remove and discard compressor hose assembly and O-rings. If the discharge muffler is mounted to the starter, the hose assembly has previously been replaced and steps 4 and 5 should not be completed.
5. Install new compressor hose assembly, P/N 1634220, (includes larger, baffled discharge muffler). Use refrigerant oil on O-rings. A new starter stud (P/N 1634280) and nut (P/N 11507036) are required to attach the discharge muffler to the starter.
6. Ensure that condenser, condenser lines and discharge and suction hoses are not grounded to the body.
For warranty purposes when performing the above steps two through six, use Operation No. T6128 at 1.4 hours (includes system recharge).