As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 3929 CLIMBING OUT OF PHILADELPHIA HAD TO RETURN TO FIELD DUE TO THE AHRS ON THE CAPTAINS SIDE GOING INOP. THE PILOT ELECTED TO RETURN TO FIELD FOR MAINTENANCE. MAINTENANCE REPLACED THE NR 1 AHRS COMPUTER AND ALL OPERATIONAL CHECKS WERE GOOD. AIRCRAFT RETURNED TO SERVICE.