As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PRE TAKEOFF RUN UP, THE MAG DROP (BOTH MAGS) WAS BEYOND LIMITS. THIS AIRCRAFT HAD A RECENT HISTORY OF RICH SERVO OPERATION FOLLOWED BY ADJUSTMENTS, WHICH WOULD NOT STABILIZE. THE SERVO WAS CHANGED. THIS PROBLEM IS COMMON ON MANY OF THE AIRCRAFT IN THIS FLEET AND HAS CAUSED FLEET-WIDE ADJUSTMENTS WHEN SUBSTANTIAL CHANGES IN ATMOSPHERIC TEMPERATURE OCCUR. IN MANY CASES THE SERVO MUST BE CHANGED WITH ONLY A FEW HOURS SINCE NEW.