What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED DUE TO: DURING FLIGHT, WHEN TESTING LIGHTS, THE LEFT MAIN GEAR LIGHTS (BOTH OVERHEAD PANEL AND NEXT TO GEAR HANDLE) DID NOT TEST. AIRCRAFT EMERGENCY LANDED SAFELY AT JFK. REMOVE AND REPLACED THE LEFT MAIN GEAR INDICATOR LIGHT ASSEMBLY, PER AMM 33-18-00. SYSTEM TESTED THE LANDING GEAR CONTROL SYSTEM, PER AMM 32-31-00. ALL LIGHT INDICATIONS TESTED GOOD IN AIR MODE AND IN GROUND MODE.