What was found
DURING LANDING, THE PILOT SELECTED THE LANDING GEAR HANDLE DOWN AND THE RED UNSAFE LIGHT IN THE HANDLE REMAINED ILLUMINATED. A MANUAL GEAR EXTENSION WAS PERFORMED, AND THE AIRCRAFT LANDED SAFELY. MAINTENANCE FOUND A DEFECTIVE DOWNLOCK SWITCH. IT WAS REMOVED AND REPLACED, MULTIPLE GEAR EXTENSION AND RETRACTION CHECKS WERE PERFORMED SUCCESSFULLY, AND THE AIRCRAFT HAS BEEN RETURNED TO SERVICE WITH NO FURTHER ISSUES.