What was found
IAH - FLIGHT 3137, THE CREW REPORTED THAT AFTER T/O THE LANDING GEAR WOULD NOT RETRACT. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE LANDING GEAR AIR/GROUND RELAY KO024, OPERATIONALLY TESTED WITH NO DEFECTS NOTED, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.