What was found
(CAN) DE-ICING SYSTEM FAILURE;DURING DESCEND "DE-ICE PRESS" CAUTION LIGHT CAME ON. POWER ADDED WITHOUT RESULT. NO GREEN LIGHT FOR THE MOST OUTER LEFT WING BOOT. CHECKLIST IN QRH PERFORMED WITHOUT RESULT. SUSPECTED BOOT PUNCTURE. TESTED IN BOTH MANUAL AND AUTO WITH NO SUCCESS. UNEVENTFULL LANDING. INVESTIGATION/ACTION; DUAL DISTRIBUTING VALVE WAS FOUND STUCK. DDV REPLACED ACCORDING AMM 30-11-16 AND DE-ICE SYSTEM TESTED CONCLUSION; THE INABILITY TO INFLATE THE BOOT WAS CAUSED BY THE INOPERATIVE DDV.MANUFACTURE: AERAZUR