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Managers suspected the switch did actually move as planned but that a piece of fibre or dust was in the way, blocking the electrical contact in the circuit. So on Monday at 1755 EDT (2155 GMT), they flipped the switch back and forth to try to dislodge the debris. They received confirmation that the fix had worked at 0540 EDT (0940 GMT) on Tuesday, when the ACS's full voltage was detected and the HRC channel in particular showed vital signs again.