What was found
AFTER GEAR HANDLE WAS MOVED UP, ALL GREEN LIGHTS STAYED ON AND ALL RED LIGHTS ILLUMINATED EXCEPT A-LEFT MAIN GEAR. GEAR WOULD NOT RETRACT. PDX SWAPPED LEFT MAIN A & B SENSOR LEADS PER SNL 20-32-0015. SWUNG GEAR. DEFERRED RED B-LIGHT IAW MEL 32-60-1A. GEAR OPS CHECK GOOD. FOUND B-UPLOCK PROX TO BE OPERATIONAL. HOWEVER, FOUND A-UPLOCK TO BE INOP. REPLACED A-UPLOCK PROX HARNESS PER MM 32-61-01. ALL GEAR INDICATIONS CHECK GOOD ON GEAR SWING.