What was found
AFTER DEPARTURE, AIRCRAFT WOULD NOT PRESSURIZE. RAN QRH AND NO SUCCESS. APPLIED SYSTEMS KNOWLEDGE AND COULD NOT SOLVE PROBLEM. RETURNED TO MEMPHIS. AFTER BLOCK-IN TO MEMPHIS, AND A VISUAL INSPECTION, FOUND AFT CARGO DOOR OPEN, AND FAIRING DOOR CLOSED. SUSPECT NO INDICATION IN COCKPIT DUE TO AFT CARGO DOOR WARNING SWITCH STUCK CLOSED. CLEANED SWITCH PER 727 M/M REF SMP'S AND CYCLED DOOR SEVERAL TIMES. ALL INDICATIONS NORMAL. OK TO CONTINUE.