As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB, LEFT DUCT PRESSURE FLUCTUATED PLUS OR MINUS 5 PSI FROM 35 PSI. RIGHT DUCT WAS STABLE AT 35 PSI AT THAT TIME. BOTH WERE STABLE AT CRUISE. ACFT GROUNDED. ACCOMPLISHED TASK CARD NG-36WC-00001. NO DEFECTS NOTED DURING HEALTH CHECK. REPLACED BLEED AIR REGULATOR IAW AMM 36-11-03. REPLACED PRSOV IAW AMM 36-11-04. OPS CHECKED NORMAL.