What was found
CENTER PEDESTAL EXTRMLY HOT TO TOUCH. GLARESHIELD TOO HOT TO TOUCH. HOT AIR COMING FR OM UNDER GLARESHIELD. UNABLE TO COOL FLIGHT DECK OBSTRUCTIONS AND OPS NORMAL. REF AMM 21-58-00Z PERFORMED FIM 21-58 FAULT 912, WITH NO INDICATION OF EQUIP COOLING ADVISORY MSG OR STATUS MSG REPORTED BY FLIGHT CREW,ACCOMPLISHED CHECKS OF NOTED ITEMS FOR EQUIPMENT COOLING SYSTEM. AIR INLET AND DISTRIBUTION DUCTS NO DEBRIS OR ADD EMP:U155524, U118140. OBSTRUCTIONS AND OPS NORMAL. REF AMM 21-58-00Z MX PERFORMED ON MULTIPLE LOG PAGES. REF LP 5286702 FOR ECM TEST. OPS CHECK GOOD. REF LP 5286739 WHERE WE PERFORMED EQUIP COOL SYSTEM TEST. R&R OF OVHT SWITCH AND OPS CHECK. LP 5286783 WHERE WE REMOVED ALL DISPLAYS AND INSPECTED FOR DEBRIS AND ADEQUATE AIRFLOW. REF LP 5284077 FOR FAULTED LH PACK TCV FAULTING. TCV R&R & OPS CHECK GOOD. REF LP 5288714 FOR OPS CHECK OF TRIM AIR MODUL ATING VALVE. OPS CHECK GOOD. REF LP 5286466 FOR R&R OF L MCDU. PERFORMED EQUIPMENT COOLIMG MONITOR TEST WITH AND WITHOUT ENGINES RUNNING REF AMM 21-58-37-810-801-C2. NO FAULTS NOTED. TO VERIFY FUNCTION OF OVHT INDICATION. DUE TO NO OPS CHECKS BEING AVAILABLE FOR THE OVHT SWITCH ITSELF, REMOVE AND REPLACE OVHT SWITCH S00041 IAW AMM 21-58-26. INSTALLED NEW OVHT SWITCH S00041 PERFORMED OVERHEAT INDICATION TEST REF AMM 21-58-00-705-122-006. NO FAULTS DETECTED PARTS USED: 64-2158-3-0006,QTY :1. DUE TO DISPLAY INDICATION ISSUES AND OVHT ISSUES PLEASE REMOVE ALL DISPLAYS AND INSPECT SCREENS FOR DEBRIS. ALSO VERIFY ADEQUATE AIRFLOW IS PRESET. REFERENCE AMM 34-22-04 FOR EHSI, 34-22-03 FOR EADI, AND 31-41-01 FOR EICAS. REMOVED ALL SPECIFIED SCREENS AND DISPLAYS, INSPECTED SCREENS. NO DEBRIS FOUND. REF AMM 34-22-04 FOR EHSI, 34-22-03 FOR EADI, AND 31-41-01 FOR EICAS. BITE TEST ON LEFT PACK TEMP CONTROLLER SHOWS LEFT PACK TEMP CONTROL VALVE FAULTING. REPLACED LH PACK TEMP CONTROL VALVE REF 21-51-12. ACCOMPLISHED INSTALLATION & LEAK CHECK OF LH PACK TEMP CONTROL VALVE REF 21-51-12-404-013, NO LEAKS OR OTHER DEFECTS NOTED. PERFORMED OPS CHECK OF THE TRIM AIR MODULATING VALVE IAW AMM 21-61-00-735-033 STEP L. TEST PASSED. WHILE TROUBLESHOOTING TECH'S, "OBSERVED NAV DISPLAY RANDOMLY SHOWING ALIGNMENT. HEADING SWINGS IRRADICALLY. ALSO SEEING GS JUMP UP AND DOWN AT THE SAME TIME. THIS IS OCCUR RING WITH THE IRU ALIGNED AND OFF. TRIED TO ISOLATE CAUSE BY PUL LING BREAKERS ON THE FOLLOWING COMPONENTS: LT CTR RT IRUS, LT AN D RT SIGNAL GENERATORS, LT CTR RT MMRS, LT RT FMC AND LT AND RT EICAS COMPUTERS. REF AMM 34-21-00/201.01 SERVICE TIP." REPLACED LH MCDU PER TECH SUPPORT REQUEST. AMM REF 34-61-02-400-802. PARTS USED: 75-3120-9-0007,QTY :1 ROTABLE PARTS CHANGE WAS INDICATED - TT # 1548527 SN OFF 5505 PANEL, MCDU, FL OFF 75-3120-9-0007 5505 ON 19-3461-9-0006 2557 PANEL, MCDU, FL OFF 75-3120-9-0007 5505 ON 0000 PERFORMED IRU OPS CHECK PER TECH SUPPORT REQ. OPS CHECK GOOD. LH MCDU OPS CHECK GOOD AS WELL IAW AMM 34-61-02-710-802. ORIGINAL SUBMISSION DATE: 7/28/2023