What was found
EN ROUTE AT FL 350, IN AND OUT OF POSSIBLE ICING CONDITIONS, WHEN INITIATING WING A/I ON, RECEIVED AIR SYS 3 OFF (LEVEL 1) ANNUNCIATED, WITH NR 3 BLEED (AMBER) AND NR 3 MANF (RED) LIGHTS ILLUMINATED. QRH PROCEDURES FOLLOWED. DIVERTED INTO TO KDEN. RED MANF LIGHT EXTINGUISHED APPROX 10 MIN FROM LANDING MEL: RELEASED FOR SERVICE PER MEL/CDL: 30-11-01 CATEGORY: C EXPIRATION: 27AUG05 WING A/I SHUTOFF VALVES, INOP. DO NOT OPERATE A/C IN ICING." PERFORMED LEAK DECAY CHECK FOR NR 3 MANIFOLD OK. CHECKED MANIFOLD FAIL DETECTOR UNIT FOR FAULTS. REPLACED NR 3 MAN FAIL DETECTOR PRESS SWITCH AND TESTED OK TO CONTINUE.