TM 1-1520-238-T-4 6–112 Change 1 6–47. OIL PSI NOSE GRBX 1 INDICATOR – IS LIGHTED WHEN HOD DISPLAYS NORMAL 6–47 NGB 1 OIL PRESSURE Tools: Nomenclature Part Number Tool Kit, Aircraft SC518099CLA01 Mechanic’s Tool Kit, Electrical SC518099CLA06 Repairer’s Adapter, Straight Pipe A1100-4-4 to Tube, Female Pipe End, 37 Flared Gage Pressure, Dial GGG76 Indicating (0-200 PSI) Multimeter, Digital AN/PSM-45 Personnel Required: 67R Attack Helicopter Repairer 68X Armament/Electrical Systems Repairer 152FG Maintenance Test Pilot References: TM 1-1520-238-T-6 TM 55–1230–476–20–2 TM 1-1520-238-23 TM 9-1230-476-20-2 WARNING Turn off power before detaching or attaching wires and connectors. High current 28 VDC or 115 VAC is present. Failure to do so could result in death or serious injury. 1. Check HOD display NGB 1 oil temperature reading. Was NGB 1 oil temperature 140 C or higher on HOD during flight? YES Go to step 3. NO Go to step 2. 2. Detach P18. Check OIL PSI NOSE GRBX 1 indicator. Does indicator remain lighted? YES Refer to TM 1-1520-238-T-6 to troubleshoot the pilot caution/warning system. NO Go to step 4. 3. Visually inspect NGB 1 for low oil level (TM 1-1520-238-23). Is damage present? YES Replace NGB 1 (TM 1-1520-238-23). NO Go to step 6. 4. Check for short between P61–D and P61–E. Does short exist? YES Replace NGB 1 low oil pressure switch (TM 1-1520-238-23). NO Go to step 5. 5. Detach P18 and P61. Check for short between J61–D and ground. Does short exist? YES Repair shorted wire between J61–D and P18–44. Go to paragraph 6–13. NO Refer to TM 1-1520-238-T-6 to troubleshoot the pilot caution/warning system. 6. Remove NGB 1 oil pressure transducer (TM 1-1520-238-23). Install pressure gage. Start engine 1 and place PWR lever to FLY (TM 1-1520-238-CL). Operate until readings stabilize. Is oil pressure above 28 LB on pressure gage? YES Go to step 7. NO Replace NGB 1 (TM 1-1520-238-23).