Dash 8-400
Confusion; Distraction; Human-Machine Interface; Time Pressure
Aircraft Equipment Problem Critical; Deviation - Track / Heading All Types
Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Environment - Non Weather Related; Procedure
We were cleared for the ILS 4R approach into EWR. I was utilizing the autopilot for the approach and at 700 feet AGL the PM called; 'approach lights' in sight. I continued to scan my PFD and noticed that the localizer started to move to the left. The autopilot quickly turned left to correct for this condition; but when I looked up; the runway lights and runway were slightly to my right. I immediately disengaged the autopilot to line up with the runway and continue a stabilized approach to landing. This seemed to be an anomaly with the reception of the localizer. The autopilot reacted as if something had gotten in between the aircraft and localizer because it is very strange that the localizer would indicate that we were right of course when the aircraft was left of course. It is important that pilots continue to hold the controls during approaches with an autopilot because of the quick reaction necessary to correct for potential hazards.
[Report contains no additional information.]
At 700 FT on an ILS final for EWR 4R; a DHC-8-400 localizer deviated left causing the autopilot to quickly follow but the First Officer disconnected the autopilot; returned to course and continued to a safe landing.