What was found
FLT 4055 - AFTER TAKEOFF GEAR UNSAFE LIGHT REMAINED ILLUMINATED AFTER GEAR WAS RETRACTED, CREW ELECTED TO RETURN TO FIELD. PIT MAINTENANCE INSPECTED AIRCRAFT AND DISCOVERED CHAFED WIRE LEFT MLG UPLOCK SWITCH HARNESS. REPAIRED CHAFED WIRE IAW MM CHAPTER 20-00-00 STANDARD PRACTICES. FUNCTIONAL CHECK FLIGHT (FCF) CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE. (W)