What was found
ON CLIMB OUT, THRU FL 350, LEFT BLEED TRIP LIGHT ILLUMINATED. RAN CHECK LIST, ON RESET, BLEED TRIP LIGHT EXTINGUISHED. LEFT DUCT DUCT PRESSURE VARIES BETWEEN 35 TO 45 PSI DURING CRUISE AT FL 320. RIGHT DUCT PRESSURE HOLDS STEADY AROUND 45 PSI DURING SAME. ACFT GROUNDED. ACCOMPLISHED BLEED AIR HEALTH CHECK T/C NG 36WC-00001, BLEED AIR REGULATOR FAILED. R & R BLEED AIR REGULATOR. LEAK CHECK GOOD REF MM 36-11-03. ACCOMPLISHED HIGH POWER REPAIR COMFIRMATION REF MM FIM 36-10 TASK 801 ITEM J. OPS CHECKS NORMAL.