What was found
LEFT MAIN 'A' SYSTEM GREEN LIGHT STAYED ON AFTER GEAR RETRACTION. RECYCLED 3 TIMES, RED TRANSIT LIGHTS DID NOT ILLUMINATE WHEN GEAR WAS PUT BACK DOWN, GREEN LIGHT WENT OUT IN BUMPS AT ABOUT 16,000 FT. RETURNED TO SLC, REPLACED BAD LEFT GEAR PROXIMITY SENSOR IN 'A' SYSTEM. SWUNG GEAR AND ALL SYSTEMS OPS AND READS NORMAL.