As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING A GROUND RUN AND HYDRAULIC CHECKS THE HYDRAULIC WARNING HORN WOULD NOT SOUND WHEN OPERATING COLLECTIVE HYDRUALIC SWITCH. HORN WOULD NOT SOUND WHEN OPERATING COLLECTIVE HYDR. SWITCH. HYDRAULICS WOULD TURN ON AND OFF, HORN WOULD NOT TURN ON. COLLECTIVE HYDRAULIC SWITCH P/N 12TTW1-3 WAS REPLACED AND HORN FUNCTIONEDPROPERLY ON AND OFF. AIRCRAFT WAS RETURNED TO SERVICE.