As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, BOTH ATTITUDE HEADING REFERENCE SYSTEM (AHRS) FAULTED. A/C RETURNED TO SJU AIRPORT AND DECLARED EMERGENCY. REPLACED NR 1 ATTITUDE HEADING REFERENCE UNIT (AHRU) AND PERFORMED OPS CHECK AS PER JIC 34-28-81 AND FOUND SYSTEM WORKING PROPERLY. (M)