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 G109 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.