What was found
ON APPROACH KSEA LOC ON CAPT SIDE ID AND LOC INTERMITTENT AND AUTO PILOT DID NOT CAPTURE UPDATE PER CAPT: WITH A/P A ENGAGED AIRCRAFT TURNED RIGHT INSTEAD OF LEFT TO CAPTURE THE LOCALIZER. LOCALIZER INDICATION ALSO INTERMITTENT ON CAPT SIDE. F/O SIDE WORKS GOOD. REPLACED NR 1 LOCALIZER ANTENNA SWITCH R315 AND ACCOMPLISHED INSTALLATION TEST, PER AMM. LOCALIZER GROUND CHECKED OK WITH NAV/COMM RAMP TEST SET.