What was found
WATER INTRUSION INTO MAGNETO CAUSING COMPLETE FAILURE; THIRD SIMILAR OCCURRENCE ON THE 1,200 SERIES MAG IN 20 MONTHS. ALL HAVE BEEN ON CONT IO520 ENGINES FRONT MOUNTED MAGS. RECOMMEND DISCONTINUE USE OF THIS MAG ON LARGE CONT ENGINES I.E., 470, 520, 550 AIRCRAFT WITH SIMILAR FAILURES C-207A, C414A.