Still stuck with the A/P not tracking the localizer. Here is a flight KDCA-KLGA, star: SWANN.GATBY until PROUD flix then ILS RWY 4, Loc 110.5, alt 2700ft. Leave KDCA on vector 076 to SWANN, 5000ft. After leaving PROUD flix, line up on localizer using A/P heading and then switch to BEAM and GLIDESLOPE ON, here the F28-4000 is not tracking the localizer (only glideslope). The GPS unit (GN340) set to direct KLGA, to show DME and activate Vloc , NOT GPS.