What was found
ON DESCENT RECEIVED LBL 1 AIR SYS 1 OFF, FOLLOWED BY LVL 2 AIR MANIFOLD 1 FAIL. REF FIM 36-23-00-810-803 AND 36-23-00-810-801. NOT:; CREW REPORTED THAT WING ANTI ICE WAS NOT IN USE AT TIME OF FAULT OCCURRENCE. FOUND LH WING ANTI-ICE PRESS SW. WAS FAULTED ON MAMIFOLD FAULT BOX IN CAC. RESET FAULT BALL. R&I LH WING DP SWITCH PER MM 36-23-03-4. PERFORMED LEAK CK AND OPS CKS OK. PERFORMED #1 PNEUMATIC PRESSURE DECAY TEST PER MM 36-00-01-5. TEST PASSED. PERFORMED AIR SYSTEM TEST PER MM 36-23-01-5. TEST PASSED. DUE HISTORY REPLACED MANIFOLD FAIL CONTROLLER PER MM 36-23-01-4. PERFORMED CONTROLLER TEST PER MM 36-23-01-5. TEST PASSED. A/C OK FOR SERVICE.