As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT THE LANDING GEAR WARNING HORN WOULD NOT TEST ON ROTARY CHECK. THE MAINTENANCE VENDOR TROUBLESHOT AND DETERMINED THAT THE ROTARY TEST SWITCH WAS DEFECTIVE. THE SWITCH WAS REPLACED WITH A NEW UNIT. OPERATIONAL CHECKS WERE SATISFACTORY. THE AIRCRAFT WAS RETURNED TO SERVICE.