What was found
GEAR DOOR OPEN LIGHT ILLUMINATED IN FLIGHT. INSPECTED AIRCRAFT MAIN LANDING GEAR DOOR UPLATCHES AND MECHANISMS IAW DC-9 AMM 32-60-03-2. ALL OKAY, NO DEFECTS NOTED. INSPECTED PROX SENSORS FOR POSITIONING AND ATTACHMENT, NO DEFECTS NOTED. REMOVED AND REPLACED LANDING PROX SWITCH CONTROL BOX IAW DC-9 AMM. OPS CHECKED GOOD. LUBRICATED MAIN LANDING GEAR DOOR UPLATCHES AND ROLLERS. ALL OKAY. (PROBLEM REPORTED OUT OF GEG EN ROUTE TO BIL) DIVERTED AIRCRAFT TO SLC. CREW RECYCLED GEAR INTO SLC, GEAR RECYCLED OKAY.