FCO BA60-F001, Airflow sensors detect power loss causing tripping

This Field Change Order (FCO BA60-F001) addresses a problem in RM VAX 6000 systems where existing airflow sensors (P/N 12-34926-01) cause "nuisance tripping" of the AC circuit breaker during power-down. This occurs because the old sensors falsely detect a loss of 12VDC power.

The FCO mandates replacing the faulty airflow sensor assembly with a new one (P/N 12-36060-01). This procedure should only be performed if the specific problem (breaker tripping on power-down) is observed. The rework involves safely powering down the system, extending the chassis, removing the top cover, disconnecting and carefully removing the old airflow sensor assembly (located at the rear of the BA60-BC chassis between the fans and card cage), and then installing the new sensor. A critical caution emphasizes that the new sensor's window must be positioned perpendicularly to the air stream to ensure proper air flow detection and prevent future circuit breaker trips. After installation, the system should be repowered, verified through self-tests, and the old sensors scrapped, with the FCO activity reported.