What was found
AT FLT 350, DUCT PRESSURE SPLIT 22 PSI. IT HAS VARIED BETWEEN 5 & 22 PSI, RT 44 PSI, LT 22 PSI ABOVE 18 PSI AND BELOW 60 PSI. ACFT GROUNDED. FOUND PRECOOLER CONTROL VALVE FAILED STEP F5, FAILED TO OPEN WHEN PC IS 3 PSI OR GREATER. REPLACED NR 1 PRECOOLER CONTROL VALVE REF AMM 36-12-02-400-801. PERFORMED INSTALLATION TEST REF AMM 36-12-02-400-801, STEP G, TEST PASSED. PERFORMED ENG BLEED CROSSOVER OPS CHECK IAW AMM 36-11-00-710-801. ALL LEVELS OF N-1 IN NORMAL RANGE.