What was found
SEA FLT 2232 - AFTER START DE-ICE PRESSURE STAYED AT 1200PSI AND A/C DID NOT PRESSURIZE FOR ABOUT 1.5 MINUTES. AFTER THAT TIME PRESSURE CAME UP TO 18PSI AND PRESSURIZATION RETURNED TO NORMAL. DURING AUTO FEATHER TEST OF ENG NR 1 DE-ICE PRESSURE RETURNED TO 12PSI AND A/C PRESSURIZATION FAILED. MX T/S AND FOUND TUBE ASSY (AIR PRESSURE LINE) FOR THE 65PSI AND 55PSI SWITCHES AT THE FIREWALL FITTING LOOSE ON THE NR 1 NACELLE. RE-TIGHTENED FITTING AND OP CHECKED BLEED AIR SYSTEM IAW DHC8-200 MM 22-11-00, PAGE 501-504, ALSO PERFORMED OP CHECKS OF THE PRESSURIZATION IAW DHC8-200 MM 21-30-00-720-801. OP CHECK GOOD ON ALL SYSTEMS. NO FURTHER DEFECTS NOTED. NO PARTS REPLACED. A/C RETURNED TO SERVICE.