What was found
PIT - BWI -FLT 1458 - AFTER TAKEOFF, THE LEFT CSD LOW OIL PRESSURE LIGHT ILLUMINATED AND THE CSD WAS DISCONNECTED. SINCE THE APU WAS ON MEL THE AIRCRAFT RETURNED TO THE FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE LEFT CSD, CSD OIL COOLER, AND LEFT GENERATOR. (M)