SUBJECT: A/C Evaporator High Pitch Whistle

NO: 24­07­95 Rev. A

GROUP: Heater & A/C

DATE: Feb. 9, 1996 NOTE: THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 24 07­95 DATED MAY 12, 1995, WHICH SHOULD BE REMOVED FROM YOUR FILES. THE PART NUMBER FOR THE A/C EXPANSION VALVE HAS BEEN REVISED AND THE 1996 MODEL YEAR HAS BEEN ADDED. ALL CHANGES ARE MARKED WITH ** ASTERISKS **.

MODELS: 1995 ­ **1996** (PL) Neon

SYMPTOM/CONDITION: Under certain conditions, the internal flow of R­134a refrigerant may set up a resonance in some evaporator cores. This resonance can emit from the dash area as a high­pitched 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 of 2,000 RPM or higher.

DIAGNOSIS: Diagnosis may be very difficult due to the intermittent nature of the whistle condition. If an ambient temperature of 85 degrees Fahrenheit or higher and high humidity are present; set the Heater­A/C controls to A/C, OUTSIDE AIR, with the temperature control at "full cool" and blower on "low". Raise the engine speed to between 2,500 to 3,000 RPM and listen for the condition to occur at the beginning of each A/C clutch cycle. If the "whistle" noise occurs, proceed to the repair procedure. If ambient temperatures of 85 degrees Fahrenheit or higher and high humidity are not present, have the vehicle owner describe in detail the conditions in which they experience the whistle. Proceed to the following diagnostic procedure. A. Verify that the A/C system is functioning properly by performing the System Charge Level procedure outlined in the 1995 Neon Service Manual (Publication No. 81­270­5025), Pages 24­7 through 24­8. B. The engine should be at normal operating temperature and the vehicle should be in a quiet location with all windows and doors closed. C. Set the Heater­A/C controls to FLOOR, RECIRC, with the temperature control at "full heat" and blower on "high heat", A/C off. D. Run the vehicle until the interior temperature reaches at least 110 degrees Fahrenheit. E. Raise the engine speed to between 2,500 to 3,000 RPM and maintain. Switch the Heater­A/C blower control to "low A/C". F. Listen for the condition to occur at the beginning of each A/C compressor clutch cycle. If the "whistle" is heard, proceed to the repair procedure.

PARTS REQUIRED: **1 5264744 Valve, A/C Expansion, With Bleed** 1 4677045 Gasket, A/C Expansion Valve To Evaporator 1 3846834 Gasket, A/C Expansion Valve To Refrigerant Line AR 82300102 R­134a Compressor Oil (PAG­ND8) AR 4797130 Coil, A/C Evaporator

REPAIR PROCEDURE: This bulletin involves installing a different type of expansion valve, the addition of extra compressor lubricant and, if necessary, the A/C evaporator coil. **1. If the vehicle is a 1996 Model Year vehicle and contains the new expansion valve (P/N 5264744) and compressor (P/N 5264745) proceed to step 19.** 2. Recover the R­134a refrigerant while completely discharging the A/C system. WARNING: THE A/C SYSTEM MUST BE COMPLETELY DISCHARGED BEFORE PROCEEDING WITH THIS OPERATION. 3. Remove the boot­type wire connector from the low pressure cutoff switch which is part of the expansion valve. 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 or damage. 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. Remove the Low Pressure Cut­off switch from the old expansion valve and install it on the **new expansion valve, P/N 5264744.** 9. Place a new gasket, P/N 4677045, on the evaporator sealing plate and install the **new expansion valve, P/N 5264744.**DO NOT SCRATCH THE SEALING SURFACES of the new expansion valve. Install the two attaching screw and torque to 70 ­ 130 in. lbs. (8 ­ 14 Nm). 10. Add two ounces of PAG­ND8, P/N 82300102, oil into the suction line. 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 Nm.). 13. Connect the wire connectors to the low pressure cut­off switch. 14. Evacuate and recharge the A/C system. Proceed to the following steps to verify that the condition has been corrected. 15. The engine should be at normal operating temperature and the vehicle should be in a quiet location with all windows and doors closed. 16. Set the Heater­A/C controls to FLOOR, RECIRC, with the temperature control at "full heat" and blower on "high heat", A/C off. 17. Run the vehicle until the interior temperature reaches at least 110 degrees Fahrenheit. 18. Raise the engine speed to between 2,500 to 3,000 RPM and maintain. Switch the Heater­A/C blower control to "low A/C". 19. Listen for the condition to occur at the beginning of each A/C compressor clutch cycle. If the "whistle" is still exists replace the A/C evaporator coil, P/N 4797130 as outlined in the Service Manual, Pages 24­23 through 24­24. NOTE: USE NEW EXPANSION VALVE GASKETS P/N 4677045 AND 3846834 BUT DO NOT REPLACE THE EXPANSION VALVE A SECOND TIME.

POLICY: Reimbursable within the provisions of the warranty.