Rear Overhead A/C - Performance Testing
NO: 24-16-98GROUP: Heating & A/C
DATE: Nov. 20, 1998
SUBJECT:
Rear Overhead Air Conditioning
Performance Testing
MODELS:
1998 - 1999 (DN) Durango
NOTE:
THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH THE REAR OVERHEAD A/C SYSTEM (SALES CODE HBA).
DISCUSSION:
The following rear overhead air conditioning performance testing information was not available in Group 24 of the 1998 and 1999 Durango Service Manuals (Publication Nos. 81-370-8116 and 81-370-9116). Please make a note in these publications to refer to this Technical Service Bulletin when diagnosing the rear overhead air conditioning system.
REAR OVERHEAD AIR CONDITIONING PERFORMANCE TEST
WARNING:
REVIEW THE SERVICE WARNINGS AND PRECAUTIONS LOCATED ON PAGES 24-3 AND 24-4 OF THE 1998/1999 DURANGO SERVICE MANUAL (PUBLICATION 81-370-8116/9116) BEFORE PERFORMING THIS PROCEDURE.
1. Measure the ambient air temperature of the repair area. DO NOT proceed unless the ambient temperature is at least 21°C (70°F).
2. Connect a tachometer and a manifold gauge set.
3. Set the heater-A/C mode control switch knob to the MAX A/C position. Set the temperature control knob to the full cool position. Set the blower motor switch knob of both the front A/C and rear overhead A/C systems to the high speed position.
4. Start the engine and hold the engine speed at 1,000 rpm with the compressor clutch engaged. If the compressor clutch does not engage, see the A/C Diagnosis And Testing chart on page 24-14 of the 1998 Durango Service Manual (Publication No. 81-370-8116) or page 24-15 of the 1999 Durango Service Manual (Publication No. 81-370-9116). Operate the engine until the engine temperature reaches it's normal operating range.
5. Close the doors and windows of the vehicle. The hood of the vehicle should be mostly closed.
CAUTION:
DO NOT STICK THE TEMPERATURE PROBE INTO THE REAR DUCT TOO FAR. THE TEMPERATURE PROBE COULD CONTACT THE BLOWER MOTOR VANES CAUSING DAMAGE TO THE BLOWER MOTOR AND/OR THE TEMPERATURE PROBE.
6. Insert a thermometer into the driver side center (panel) A/C outlet for testing of the front A/C system. Hold a thermometer at the rear overhead A/C right center outlet for testing of the rear overhead A/C system. Operate the engine for five minutes.
7. With the compressor clutch engaged, record the discharge air temperature of the driver side center (panel) A/C outlet and the right center outlet of the rear overhead A/C system. Then, record the compressor discharge pressure (HIGH SIDE - Port located on the liquid line near the front of the vehicle) and the compressor inlet pressure (LOW SIDE - Port located on the compressor suction line at the compressor). The compressor may cycle depending upon the ambient temperature and humidity. If the clutch cycles, obtain the readings just before the clutch disengages.
8. Compare the discharge air temperature reading to the Performance Temperature and Pressure Chart.
9. If the discharge air temperature exiting the driver side center (panel) A/C outlet for the front A/C system is normal and the discharge air temperature exiting the rear overhead A/C right center outlet is high, inspect the following:
^ Test the rear overhead A/C expansion valve. Refer to the 1998 and 1999 Durango Service Manuals (Publication Nos. 81-370-8116/9116), pages 24-24 and 24-25 for the 1998 manual and pages 24-25 and 24-26 for the 1999 manual.
^ Inspect the rear overhead A/C evaporator coil for an internal restriction or blockage.
10. Compare the Compressor Inlet Pressure (LOW SIDE) and Compressor Discharge Pressure (HIGH SIDE) pressure readings to the Performance Temperature and Pressure chart. If the pressures are abnormal, refer to the A/C Diagnosis And Testing chart on pages 24-14 and 24-15 of the 1998 Durango Service Manual (Publication No. 81-370-8116) or pages 24-14 through 24-16 of the 1999 Durango Service Manual (Publication No. 81-370-9116).
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