What was found
APU FAULT LIGHT DURING STAT. RAN QRH AND WAITED 4 MINUTES; LIGHT EXTINGUISHED. TRIED RESTART AND FAULT LIGHT ILLUMINATED AGAIN. ACFT GROUNDED. INTERROGATED CDS FOR APU FAULTS, FOUND MESSAGE 49-41011 NO FLAME SHUTDOWN. FOLLOWED FIM 49-40-00-810-802. REPLACED APU EXCITER, IGNITOR, AND LEAD. REF AMM 49-41-31, 49-41-51, AND 49-41-52. OPS CHECK OF APU GOOD. STARTS NORMAL. AIRCRAFT CLEAR OF MEL 49-1B.