Initial Inspection and Diagnostic Overview

1. Verify the customer's concern by operating the climate control system to duplicate the condition.

2. Inspect to determine if one of the following mechanical or electrical concerns apply:

VISUAL INSPECTION CHART

Mechanical
- Loose, missing or damaged A/C compressor drive belt.
- Loose or disconnected A/C clutch.
- Loose, misrouted or damaged vacuum lines.
- Broken or leaking vacuum control motor.
- Broken or leaking refrigerant lines.

Electrical
- Open fuses.
- Blower motor inoperative.
- A/C compressor inoperative.
- Circuitry open/shorted.
- Disconnected electrical connectors.

a. A leak in the vacuum control circuit will send all airflow to the defroster outlets. This condition may occur during acceleration (slow leak), may exist at all times (large leak), and may exist only when specific functions are selected (indicating a leak in that portion of the circuit). The vacuum hoses used in the passenger compartment control circuit are constructed from PVC plastic material. The vacuum hoses used in the engine compartment are constructed of Hytrel(R). Because of the materials used, never pinch the vacuum hoses off during diagnosis to locate a leak. A wood golf tee can be used as a plug when it is necessary to plug one end of a vacuum hose for leak test purposes.

3. If the inspection reveals obvious concern(s) that can be readily identified, repair as required.

4. If the concern remains after the inspection, connect the Rotunda New Generation Star (NGS) Tester to the Data Link Connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the NGS tester menu. If the NGS tester does not communicate with the vehicle:
- check that the program card is properly installed.
- check the connections to the vehicle.
- check the ignition switch position.

If the NGS tester still does not communicate with the vehicle, refer to the New Generation Star Tester manual.

5. Perform the DATA LINK DIAGNOSTIC TEST using the NGS tester. If the NGS tester responds with:
- CKT 914 and CKT 915 = All module NO RESP/NOT EQUIP, go to Communication System Diagnostics in Information Bus.
- If the Powertrain Control Module (PCM) is not listed for a communication concern, turn the A/C function selector switch to OFF and execute Self-Test Diagnostics for PCM.

6. If the DTCs retrieved are related to the concern, go to the Powertrain Control Module (PCM) Diagnostic Trouble Code (DTC) Index to continue diagnostics. With Electronic Climate Control

7. If no DTCs related to the concern are retrieved, go to the Symptom Chart to continue diagnostics. Symptom Related Diagnostic Procedures