What was found
PER CAPT: WHEN GEAR HANDLE SELECTED DOWN, GEAR HANDLE ARROWS SCROLLED, GEAR DOORS CONTINUOUS CYCLING ON ECAM, BOTH LGCIU'S SHOWED DISAGREE, 3 REDS FOR GEAR DOWN, THE N LGCIU 1 FAULT, ECAM PROMPT "GRAVITY GEAR EXTEND". EXTENDED GEAR MANUALLY, THEN 3 GREENS FOR GEAR DOWN. PFR INDICATES SENSOR 20GA AS THE PROBLEM. REPLACED SNSR 20GA PER AMM 32-31-73-200-001-A. CYCLED LANDING GEAR SEVERAL TIMES PER AMM 32-31-00-720-002-A, AND PERFORMED FREE-FALL EXTENSION PER AMM. NO FAULT.