The air conditioning system is not working. The A/C lights and switches operate correctly, but there is no cold air output. The vehicle has been sitting for several years and had a flat battery.

The A/C system was inoperative despite electrical controls appearing functional. The system contained refrigerant, and fuses and relays were intact. Initial diagnosis showed the A/C relay would click when commanded through the scan tool, but the compressor clutch would not engage. A direct bridge of the relay circuit engaged the compressor, confirming the clutch could operate. Fault codes P0646 (A/C compressor clutch relay input low), P1481 (electronic fan relay 1), and P1613 (serial communication with ASC) were present.