A/C Evaporator - High Pitched Whistle Noise
NO: 24-12-94GROUP: Heater & A/C
DATE: Jul. 8, 1994
SUBJECT:
A/C Evaporator High Pitch Whistle
NOTE:
THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 24-30-93, DATED DEC. 3, 1993. THIS IS A COMPLETE REVISION, AND COPIES OF TECHNICAL SERVICE BULLETIN 24-30-93 IN YOUR FILES AND/OR THE 1993 TECHNICAL SERVICE BULLETIN MANUAL (PUBLICATION NO. 81-699-94000), SHOULD BE NOTED TO REFER TO TECHNICAL SERVICE BULLETIN 24-12-94.
MODELS:
1993 - 1994 (AS) Town & Country/Caravan/Voyager
NOTE:
THIS BULLETIN APPLIES TO VEHICLES BUILT WITH P/N 4677203 EXPANSION VALVES. THE PART NUMBER IS STAMPED ON THE EXPANSION VALVE NEXT TO THE LOW PRESSURE CUT-OUT SWITCH. A DIFFERENT TYPE OF EXPANSION VALVE HAS BEEN USED IN VEHICLE PRODUCTION SINCE APPROXIMATELY 11/93 FOR 2.5L ENGINE EQUIPPED VEHICLES, 3/94 FOR 3.3L AND 3.8L ENGINE EQUIPPED VEHICLES. THE DIFFERENT TYPE OF EXPANSION VALVE WILL BE USED AT THE START OF THE 1995 MODEL YEAR FOR 3.0L ENGINE EQUIPPED VEHICLES.
SYMPTOM/CONDITION:
Under certain conditions, the internal flow of R-134a refrigerant may set up a resonance in some evaporator cores. This resonance can emit from the dash area as a high-pitched whistle noise. The whistle noise usually lasts 3 to 5 seconds and starts shortly after the A/C compressor clutch engages. The duration and the intensity of the whistle noise may vary as well as be highly intermittent. The whistle noise is most likely to be experienced in ambient temperatures above 85 degrees Fahrenheit and engine speeds around 2000 RPM.
DIAGNOSIS:
Diagnosis may be very difficult due to the intermittent nature of the whistle condition. If ambient temperatures in excess of 85 degrees Fahrenheit are not present for test drive purposes, have the vehicle owner describe in detail the condition(s) in which they experience their concern to determine if this bulletin applies.
PARTS REQUIRED:
1 4677334 Valve, A/C Expansion
1 4677045 Gasket, A/C Expansion Valve To Evaporator
1 3846834 Gasket, A/C Expansion Valve To Refrigerant Line
REPAIR PROCEDURE:
This bulletin involves installing a different type of expansion valve.
1. Recover the R-134a refrigerant while completely discharging the A/C system.
WARNING:
THE A/C SYSTEM MUST BE COMPLETELY DISCHARGED BEFORE PROCEEDING WITH THIS OPERATION.
2. Remove the boot-type wire connector from the low pressure cut-off switch.
3. Remove the 3-pin connector from the Electronic Cycling Clutch Switch (ECCS).
4. Remove the bolt in the center of the refrigerant line sealing plate.
5. Carefully pull the refrigerant line sealing plate from the expansion valve.
6. Cover the openings on refrigerant line sealing plate to prevent contamination.
7. Remove the two screws attaching the expansion valve to the evaporator sealing plate.
8. Carefully remove the expansion valve and the two aluminum gaskets.
9. Place a new gasket (P/N 4677045) on the evaporator sealing plate.
10. Carefully hold the new expansion valve (P/N 4677334) to the evaporator sealing plate, DO NOT SCRATCH THE SEALING SURFACES. Install the two attaching screws and torque to 70 - 130 in.lbs. (8-14 N-m).
11. Place a new gasket (P/N 3846834) on the refrigerant line sealing plate.
12. Carefully hold the refrigerant line sealing plate to the expansion valve, DO NOT SCRATCH THE SEALING SURFACES. Install the attaching bolt and torque to 170 - 230 in.lbs. (20 - 26 N-m.).
13. Connect the wire connectors to the low pressure cut-off switch and the ECCS.
14. Evacuate and recharge the A/C system.
POLICY: Reimbursable within the provisions of the warranty.
TIME ALLOWANCE:
Labor Operation No: 24-35-20-90 0.8 Hrs.
FAILURE CODE: P8 - New Part