What was found
MAIN CARGO DOOR LIGHT CAME ON INFLT . BOTH PACKS TURNED OFF . ALT 6000 FT PSI DIFF. 2.8 . LIGHT WENT OUT ONCE DEPRESS. COMPLIED WITH CHECKLIST RETURN TO MCO . OPERATED MCD OPEN/CLOSED SEVERAL TIMES. CLOSED DOOR AND PRESSURIZED A/C. WAS ABLE TO GET DOOR WARN RED TO COME ON WITH DOOR CLOSED AND BARBER POLE IN LINE. VISUALY INSPECTED AND CHECKED LOCKROD SWITCH AND ALL THE LATCH WARNING SWITCHES. MOST FWD LATCH SWITCH WAS CAUSING THE LIGHT TO COME ON WITH DOOR CLOSED. REPLACED AND ADJ FWD LATCH WARNING SWITCH. OPERATED DOOR OPEN/CLOSE SEVERAL TIMES. OPS CHECK OK. PRESSURIZED TO 3 PSID WITH NO MCD WARNING LIGHT.