# SDR ASAA2021010933845

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: January 9, 2021
- Submitted: January 12, 2021
- Operation: Air carrier
- Aircraft: [N492AS](https://openairdocs.org/aircraft/N492AS), registered now
- Make and model: Boeing 737990ER
- Aircraft serial: 44110
- Aircraft time: 19,415 hours, 6,230 cycles
- System (JASC): [2160 · Cabin Temperature Control System](https://openairdocs.org/jasc/2160)
- Part: Modulating Valve
- Part number: 3989085
- Part serial: 24599
- Condition: Faulted
- Location: Left Ecs Bay
- Part time: 20,242 hours, 6,489 cycles
- Stage of operation: TX
- 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/ASAA2021010933845

## Discrepancy

CONT CAB "ZONE TEMP" CAUTION LIGHT AFTER PUSHBACK AND ENGINE START.  CLEARS UPON PRESSING MASTER CAUTION PUSH TO RESET.  GROUNDED-YES.  CONFIRMED LIGHT ON RECALL.  PERFORMED PZTC BITE, REF B737-900 AMM 21-61-00.  PZTC NR 2 SHOWS FLIGHT DECK TRIM VALVE FAULT ON BIT AND PREV FLIGHT, FAULT CLEARS ON VERIFY.  DUE TO HISTORY ON 01/03/21, REMOVED AND REPLACED CONT CABIN TRIM AIR MODULATING VALVE, REF B737-900 AMM 21-61-21.  OPERATION CHECKS GOOD, REF AMM 21-61-00.  LEAK CHECK GOOD, ETOPS GROUND VERIFICATION SUCCESSFUL.

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