What was found
00-22 AT CR FL 310 SEL, WING ANTI-ICE ON, HAD NR 1 MANIFOLD FAILURE LIGHT ILLUM. PNEU SUPPLY OFF FOR NR 1 ON FOR 2/3, ISOL VLV 1-2 OPEN AT TIME OF FAILURE. REMOVED AND REPLACED NR 4 L/E SLAT PER DC10-30 MM 27-80-01-4-2, LEAK AND OPS CK GOOD. INSTALL NR 4 SLAT PER EA 8-3011-49033.