WAS AT RED LIGHT. NOTICED SMOKE FROM UNDER HOOD. PULLED TO SIDE OF ROAD & LIFTED HOOD. NOTICED FLAMES AROUND THE ALTERNATOR. ANOTHER MOTORIST SMOTHERED FLAMES WITH BACK PACK. VEHICLE TOWED TO SERVICE STATION. WAS INFORMED BY MECHANIC ALTERNATOR & WIRING HARNESS HAD TO BE CHANGED TO ALTERNATOR CAUGHT ON FIRE & MELTED WIRES. *AK