What was found
DURING CLIMB, GEAR UNSAFE LIGHT CAME ON. ISOLATED PROBLEM TO LEFT MAIN LANDING GEAR DOOR. CYCLED LANDING GEAR, LIGHT REMAINED ON. GEAR UPLATCH CHECK WAS OK. REPLACED PROXIMITY SWITCH BOX AND PERFORMED PROXIMITY SWITCH CONTROL BOX BYTE TEST OF SYSTEM AND CIRCUITRY PER DC-8 SUPP. M.M.