Neon L4-2.0L SOHC (1995)
Expansion Valve: Customer Interest
A/C Evaporator - High Pitched Whistle
NO: 24-07-95 Rev. A
GROUP: Heater & A/C
DATE: Feb. 9, 1996
SUBJECT:
A/C Evaporator High Pitch Whistle
NOTE:
THIS BULLETIN SUPERSEDES TECHNICAL SERVICE BULLETIN 24-07-95 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 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 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 Heater-A/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. 81-270-5025), Pages 24-7 through 24-8.
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 Heater-A/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 Heater-A/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
R-134a Compressor Oil (PAG-ND8)
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 R-134a refrigerant while completely discharging the A/C system.
