What was found
DURING GROUND COOLING IN CLT, THE FLIGHT ATTENDANT NOTED A TRACE OF SMOKE IN THE CABIN. PACK WAS ADJUSTED TO WARMER TEMP AND PROBLEM ENDED. ON TAKEOFF, THE SMOKE RETURNED AND CAUSED THE FORWARD LAV SMOKE DETECTOR TO ALARM FOR ABOUT 3 MINUTES THEN CEASED. THERE WERE NO OTHER PROBLEMS FOR THE REMAINDER OF THE FLIGHT. LANDING AT MSP WAS UNEVENTFUL. MAINTENANCE REPLACED THE APU FOR LEAKING OIL AND BOTH WATER SEPARATORS DUE TO OIL CONTAMINATION. AIRCRAFT RETURNED TO SERVICE.