What was found
IN CRUISE FROM DAY TO MCI, THE MAIN CARGO SMOKE DETECTOR LIGHT ILLUMINATED. AIRCRAFT MADE UNSCHEDULED LANDING STL. DURING DESCENT THE WARNING LIGHT EXTINGUISHED. NO EVIDENCE OF FIRE NOTED. TESTED CARGO SMOKE DETECTION SYSTEM PER MM 26, SYSTEM CHECKS NORMAL. COULD NOT DUPLICEATE DISCREPANCY. SUSPECT CONDENSATION IN CARGO HOLD GAVE FALSE WARNING. NO PARTS CHANGED.