A/C Performance - Diagnostic Procedure
NO: 24-15-95GROUP: Air Conditioning
DATE: Nov. 24, 1995
SUBJECT:
Intermittent A/C or Poor A/C Performance Diagnostic Procedure
MODELS:
1993 - 1996 (LH) Concorde/Intrepid/Vision/LHS/New Yorker
DISCUSSION:
A prioritized approach has been developed to diagnose and repair LH vehicles experiencing intermittent A/C or poor A/C performance. This Technical Service Bulletin (TSB) serves as a check list to follow. Previous TSB's are listed as reference tools for additional diagnosis and necessary repairs.
DIAGNOSIS:
I. Check engine and climate control Diagnostic Trouble Codes (DTC's) using Scan Tool (DRB III).
1. If an "A/C High Pressure" or "A/C Sensor Voltage Input High" DTC is present replace A/C pressure transducer with A/C Pressure Transducer Service Kit, P/N 4798874.
2. If "Evaporator Sensor Failure" DTC's are present replace Evaporator Sensor, P/N 4596078.
II. Using a DRB III with engine at idle, monitor A/C system pressure transducer under high sun or heat load (A/C on, lowest temperature setting, high blower, outside air, panel mode). If the readings using DRB III are taken during system malfunction and both high and low pressure fault readings are above 439 psi, verify readings with a gauge set by monitoring compressor discharge pressure. If a lower (200-300 psi) pressure reading is read by a gauge set, replace the A/C Pressure Transducer, P/N 4798874.
III. Perform built in climate control self diagnostics (calibration) at manual or ATC control heads. This procedure is outlined under MANUAL and ATC AIR CONDITIONING SYSTEM SELF-DIAGNOSTICS.
1. Manual system - A failure in the calibration procedure indicates that a problem is present in an actuator, actuator wiring and/or control head. Use analysis methods in Manual System Self-Diagnostics to troubleshoot root cause and repair or replace necessary part(s).
2. ATC system - A failure in the calibration procedure will display DTC's present in the body controller. DTC's related to the ATC system will appear on the display in numerical form. Interpretation of the trouble codes is located under ATC System Self-Diagnostics. Repair as necessary.
IV. Using the DRB III on ATC systems only, verify that the A/C system is functioning as designed. If DTC's are present, record them and repair as necessary. If no DTC's are present and Body Control Module (BCM) P/N 4605218, contains software version 7.4, replace BCM with P/N 4759227 or later, containing software 7.5 or later. Calibrate the ATC system as described under ATC System Self-Diagnostics.
NOTE:
BEFORE PROCEEDING PERFORM THE DRB III CHECK PARTIAL CHARGE TEST.
V. Perform R134a leak detection as described in TSB 24-13-94, dated Sep. 9, 1994. The most accurate way to check the evaporator is to sniff through the evaporator probe location. The evaporator probe cap should be removed (do not remove the probe itself) by removing the right under panel silencer and disconnecting the wiring connector to the probe. For difficult to find refrigerant leaks, Professional Service Equipment (PSE) R134a Refrigerant Leak Detection Dye, P/N BG-71224, is recommended (use with PSC A/C System Dye Injector, P/N BG-734). Instructions are included with the dye.
VI. The thermal expansion valve can fail in three different positions (open, closed or restricted). The open position will result in a noisy compressor or no cooling and high suction pressure. The closed position will result in low suction pressure and no cooling. The restricted position will result in low suction pressure and no cooling. In each case the thermal expansion valve will have to be replaced.
POLICY: Information Only