What was found
SEA FLIGHT 2316: ALT FAIL MESSAGE BOTH NR 1 AND NR 2 PFD. MAINTENANCE FOUND NLG STRUT OVER-SERVICED CAUSING ASSOCIATED EQUIPMENT MALFUNCTION. SERVICED NLG STRUT IAW AMM 12-10-32. ALT FAIL MESSAGE WENT AWAY AND DID NOT REOCCUR. PERFORMED ADU NR 1 AND NR 2 SELF TEST. NO PROBLEMS NOTED. AIRCRAFT OK FOR CONTINUED SERVICE. AIRCRAFT REMAINS CAT 3 LLM PLACARD REFLECTS SAME. NO PARTS CHANGED. AIRCRAFT RETURNED TO SERVICE.