# SDR ASAA2020121733705

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: December 17, 2020
- Submitted: December 22, 2020
- Operation: Air carrier
- Aircraft: [N407AS](https://openairdocs.org/aircraft/N407AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 41731
- Aircraft time: 30,864 hours, 9,749 cycles
- System (JASC): [2612 · Fire Detection](https://openairdocs.org/jasc/2612)
- Part: Fire Detector
- Part number: 90201301
- Condition: False Activation
- Location: Apu Bay
- Stage of operation: CL
- How discovered: O
- Nature of condition: N
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/ASAA2020121733705

## Discrepancy

DURING CLIMBOUT (APU OFF) APU OVHT/DETR LIGHT ILLUMINATED MOMENTARILY THEN INTERMITTENTLY THE REST OF THE FLIGHT.  GROUNDED-YES.  C/W ENGINE/APU FIRE DETECTION CONTROL MODULE BITE PROCEDURE, REF B737-900 FIM 26-10 TASK 801.  FOUND UPPER LOOP FAIL LIGHT CODE ILLUMINATED.  FAULT CONFIRMATION, REF FIM 26-10 TASK 808.  CHECKED RESISTANCE OF ALL LOOPS, FOUND TAIL PIPE AND LOWER LOOPS WITHIN LIMITS, CONFIRMED UPPER LOOP IS OPEN.  REPLACED THE UPPER OVERHEAT DETECTOR ASSEMBLY, REF B737-900 AMM 26-15-01-000-801/400-801.  ALL TEST PASS.

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