With HVAC System - Automatic - Electronic Controls

PERFORM BEFORE BEGINNING SYSTEM DIAGNOSIS
1. If the A/C Compressor Clutch engages but only warm air is delivered, disconnect the negative battery cable for 15 seconds before attempting further diagnosis. This will reset the Heater/Vent/Air Conditioning (HVAC) Programmer and may correct the problem.
2. Make sure A/C Compressor Clutch connector terminals are free from corrosion. Make sure connector is on tight.
3. Make sure grounds G105 (VIN J), G109 (VIN P) and G201 are clean and tight.
4. Make sure A/C System is properly charged with refrigerant.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (Refer to General Troubleshooting Procedures). Diagnostic Aids
^ Refer to System Diagnosis. System Diagnosis