What was found
BLEED TRIP OFF LIGHT COMES ON DURING CLIMB LIGHT NO. 1 LEFT BLEED TRIP OFF DURING CLIMB DEBREIFED PILOTS AT THE GATE. THEY STATED THAT BETWEEN 14000 AND 15000FT DURING THE CLIMB THAT THE #1 BLEED TRIP LIGHT ILLUMINATED. CREW WAS UNABLE TO RESET AND THEREFOR ELECTED TO RETURN TO FIELD. THIS FAULT HAS HISTORY. PERFORMED BLEED SHIFT AT PART POWER REF AMM 71-00-00-700-813-F00 L/H ENGINE BLEED SHIFTED NORMALLY AND REGULATED AT 45PSI OPS CHECK GOOD AT THIS TIME. ALERTED {36-0051-S870} *UNREGULATED LEFT DUCT PRESSURE LOW* (4 PSI) DURING CLIMB AT 96% N1. PRECOOLER TEMP AROUND 420F RIGHT DUCT PRESSURE AT 40PSI. PCCV 390 SENSOR REGULATING NORMAL. PLS PERFORM VISUAL INSP OF THE SENSE LINES/B-NUTS ASSOCIATED WITH PRSOV,BAR,450 SENSOR ARE DAMAGE FREE & SECURED. REF AMM 36-11-00-710-801 STEP G. TO FOCUS ON PRSOV/BAR PNEUMATIC HEALTH CHECK. IF ALL TEST PASSED,REPLACE THE 450 SENSOR REF AMM 36-11- 05-400-801.NOTE:THIS IS A REPEAT WRITE-UP PLS REVIEW HISTORY FOR PREVIOUS PARTS INSTALLED. RE-ASSIGNMENT OF THIS ITEM REQUIRES TOMC SR MGR AND LINE PLANNING OM APPROVAL. REPLACED #1 ENGINE 490 DEG F OVERTEMPERATURE SWITCH . REF AMM 36-11-08-400-801 REPLACED 390 SENSOR . WAITING PACKING FOR REDUCER . REF AMM 36-12-03-400-801 . REMOVED 450 F THERMO . RECIEVED AND INSTALLED SHORTLY AFTER THIS WRITE-UP WAS ISSUED, A/C EXPERIENCED A LEFT BLEED TRIP OFF DURING CLIMB AND AIR RETURNED BACK TO THE GATE.