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. [a]
- Broken or leaking vacuum control motor. [a]
- Broken or leaking refrigerant lines.
- Obstructed in-car temperature sensor.

[a] A leak in the vacuum control circuit 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 en of the vacuum hose for leak test purposes.

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

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 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 menu. If the vehicle selection cannot be entered:
- Check that the program card is properly installed.
- Check the connections to the vehicle.
- Check the ignition switch position.

If the NGS still does not allow with the vehicle selection to be entered, refer to the New Generation Star Tester manual.
5. Perform the DATA LINK DIAGNOSTIC TEST using the NGS. If the NGS responds with:
- CKT 914 and CKT 915 ALL MODULE NO RESPONSE/NOT EQUIPPED, go to Communication System Diagnostics in Information Bus to diagnose network concern.
- If the Powertrain Control Module (PCM) is not listed for a communication concern, turn the A/C controls to OFF and execute self-test diagnostics for the PCM.
- If equipped with EATC, and the EATC module is not listed for a communication concern, execute self-test diagnostics for the EATC module.
6. If any PCM or EATC DTCs are retrieved, and are related to the concern, go to:
- The Powertrain Control Module Diagnostic Trouble Code (DTC) Index
- or, the Electronic Automatic Temperature Control (EATC) Module DTC Index With Electronic Climate Control to continue diagnostics.
7. If no DTCs related to the concern are retrieved, go to the:
- Symptom Chart Symptom Related Diagnostic Procedures to continue diagnostics.

8. If the electronic automatic temperature control module cannot be accessed by the NGS, A: No Communication With EATC Module