What happened
While descending through 12,000 feet, the captain reported that the aircraft experienced an uncommanded roll to the left. At the time of the event, the 'A' system autopilot was engaged and the aircraft was maintaining an airspeed of 250 knots.
In response to the roll, the pilot disengaged the autopilot and manually rolled the airplane to wings-level flight. The flight continued normally with the autopilot remaining in the off position.
The investigation
A post-incident examination of the aircraft identified an intermittent electrical connection within the 'A' autopilot circuit. Investigators determined that pin connectors had been pushed out of place on the flight control computer shelf connector. Specifically, one of the pins was located in the aileron position sensor excitation circuit.
Records indicated that the 'A' flight control computer had been removed and reinstalled the day before the incident as part of an inspection of the rack for fluid contamination.