What was found
GEG FLIGHT NR 2371: AFTER TAKEOFF, HAD A RED NOSE AND HANDLE LIGHT ILLUMINATED. DID ALTERNATE GEAR EXTENSION. HAD NO GREEN WITH RED NOSE AND HANDLE STILL ILLUMINATED. ALTERNATE INDICATOR WAS SHOWING GREEN (3). AIRCRAFT RETURNED TO FIELD. MAINTENANCE INTEROGATED PSEU AND NOTED PRESENT FAULT NGLK1 PROX SENSOR OPEN. REMOVED SENSOR NGLK1 HARNESS ONLY IAW 32-21-11-000-801. INSTALLED NEW HARNESS IAW 32-21-11-400-801, NGLK1 SENSOR ONLY, UP TO AND INCLUDING 5.H. OPS CHECK OF PRIMARY EXTENSION AND RETRACTION SYSTEM CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.