# SDR AALA202604229887

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: April 20, 2026
- Submitted: April 22, 2026
- Operation: Air carrier
- Aircraft: [N943AN](https://openairdocs.org/aircraft/N943AN), registered now
- Make and model: Boeing 737823
- Aircraft serial: 30599
- Aircraft time: 70,908 hours, 30,088 cycles
- System (JASC): [2822 · Fuel Boost Pump](https://openairdocs.org/jasc/2822)
- Part: Pressure Switch
- Part number: 21C1321
- Condition: Defective
- Location: Zone 100
- Stage of operation: CR
- How discovered: V
- Nature of condition: J, S
- Precautionary procedure: O
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/AALA202604229887

## Discrepancy

AIRCRAFT WAS GROUNDED: IN CRUISE WHILE CROSS FEEDING TO BALANCE FUEL, THE NUMBER 1 AFT LOW PRESSURE LIGHT DID NOT ILLUMINATE WHEN THE SWITCH WAS TURNED OFF. ALSO, THE MASTER CAUTION DID NOT ILLUMINATE. TROUBLESHOT ISSUE PER FIM 28-22-00-810-803. FOUND NUMBER 1 AFT PUMP SWITCH S4 TO BE DEFECTIVE. REMOVED AND REPLACED S4 SWITCH, PER AMM 28-22-43 & SWPM 20-83-11. OPS CHECK GOOD AT THIS TIME.

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