As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT WAS CARRYING OUT THE HYDRAULIC TEST OF THE ACCUMULATORS AND THE HORN WOULD NOT ACTIVATE. THE A/C WAS SHUT DOWN AND AN ENGINEER STARTED TO TROUBLESHOOT. IT WAS DISCOVERED THAT THE HYDRAULIC CUT-OFF SWITCH WAS OPERATING INTERMITTENTLY. DUE TO HYDRAULIC PROBLEMS IN THE AS350 WORLD A/C GROUNDED UNTIL SERVICEABLE PART ARRIVED.