# SDR ASAA2019093025843

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: September 25, 2019
- Submitted: October 3, 2019
- Operation: Air carrier
- Aircraft: [N453AS](https://openairdocs.org/aircraft/N453AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 36354
- Aircraft time: 22,600 hours, 7,287 cycles
- System (JASC): [2613 · Overheat Detection](https://openairdocs.org/jasc/2613)
- Part: Overheat Loop
- Part number: 90202001
- Condition: Failed
- Location: Apu Bay
- Stage of operation: IN
- How discovered: C
- Nature of condition: L
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2019093025843

## Discrepancy

APU DETECTOR INOPERATIVE LIGHT. GROUNDED - YES. CONFIRMED FAULT, APU WILL NOT TEST. ACCOMPLISHED APU FIRE DETECTION LOOP RESISTANCE,  SYSTEM TESTED IAW AMM 26-15-00-730-801 & RE-CONFIRMED APU TAIL PIPE OVERHEAT DETECTOR ASSY M1925 WAS DEFECTIVE,  SHOWS 1.7M OHM INSTEAD OF 3.94K OHMS.   REMOVED & REPLACED THE M1925 OVERHEAT DETECTOR ASSY IAW AMM 26-15-01. APU FIRE DETECTION OPS CHECKED NORMAL IAW AMM 26-15-00-710-801.

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