# SDR ASAA2019121191567

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: December 9, 2019
- Submitted: December 12, 2019
- Operation: Air carrier
- Aircraft: [N442AS](https://openairdocs.org/aircraft/N442AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 43293
- Aircraft time: 23,811 hours, 7,701 cycles
- System (JASC): [4940 · APU Start/Ignition System](https://openairdocs.org/jasc/4940)
- Part: Exciter
- Part number: 38880587
- Part serial: 131296
- Condition: Inoperative
- Location: Apu
- Part time: 3,588 hours, 6,001 cycles
- Stage of operation: NR
- How discovered: O
- Nature of condition: J
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2019121191567

## Discrepancy

PER FLIGHT CREW REPORT APU WOULD NOT START FAULT LIGHT ILLUMINATED. GROUNDED - YES. PERFORMED APU BITE PROCEDURE REF B737-900 FIM 49-60 TASK 801 FOUND MX MESSAGE 49-41184 IN CURRENT STATUS. COMPLIED W/ FIM 49-40 TASK 804 THRU STEP F(4) NO ISSUES FOUND W/ WIRING HARNESS. C/W VISUAL INSPECTION OF TAIL CONE AREA NO DEFECTS NOTED. REMOVED AND REPLACED APU IGNITION UNIT IAW B737-900 AMM 49-41-31. APU OPS CHECK OK.

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