FLC OF A B767-300ER MAKING AN APCH TO LAX AFTER FLYING FROM LHR HAS RWY CHANGE TO RWY 25L INSTEAD OF RWY 25R. THEY HAD THE WRONG LOC FREQ AND APCH CTLR CAUGHT THE ERROR AND CORRECTED THEM BACK TO LINE UP WITH THE RWY.

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DEPARTED LONDON (LHR) WITH ABOUT 10 HRS 50 MINS SCHEDULED FLYING TIME; NONSTOP TO LAX ARPT. WE WERE ALL SOMEWHAT UNFAMILIAR WITH WEST COAST FLYING. THAT; AND A LONG FLT FROM EUROPE; PROBABLY HELPED TO CONTRIBUTE SOME ERROR WITH AN ILS APCH TO RWY 25L AT LAX ARPT. AT ABOUT 7000 FT MSL AND 21 DME; WE WERE CLRED FOR THE APCH TO RWY 25L AND SWITCHED THE LOC FREQ TO THAT RWY; FROM WHAT HAD BEEN ORIGINALLY SET UP (ILS RWY 25R). THOUGH HAND FLYING AT THE TIME; THE LOC 'LOCK-ON' COMMANDED A TURN TO THE R; ABOUT 20 DEGS! AS WE BEGAN TO CHK FOR WHAT MIGHT BE THE PROB; WE WERE IMMEDIATELY GIVEN A 230 DEG HDG TO RECAPTURE THE RWY 25L LOC FROM THE APCH CTLR; AND DOING SO; WERE THEN GIVEN ANOTHER 'STEER' TO THE NW OF 20 DEGS (BY THE FLT GUIDANCE SYS)! THE SCENARIO WAS: 1) SOME FATIGUE DUE TO LONG FLT TIME AND 'ON DUTY TIME.' 2) REASSIGNED TO FLY TO AN ARPT 'OFF THE NORMAL RTE.' 3) A MARGINAL 'VFR CONDITIONS' WITH THE AFTERNOON SUN BEATING INTO THE COCKPIT; WHICH MADE SOME DIFFICULTY IN CATCHING WHAT THE PROB WAS. WE HAD ALL CHKED FOR THE CORRECT LOC FREQ 'RESET' FOR RWY 25L (GOOD IDENT); BUT FAILED TO CATCH THE 269 DEG FRONT COURSE SETTING IN THE STRONG AFTERNOON SUNLIGHT. A RESET TO 249 DEGS GOT US ONTO THE RWY 25L LOC OK; BUT NOT BEFORE SOME CONFUSION. I HAD VERIFIED THE 249 DEG FRONT COURSE IN THE WINDOW; AS FAR OUT AS LAS; BUT THEN BECAME BUSY DURING THE APCH AND DID NOT CATCH THE MISSET OR CHANGE. I FEEL THAT FATIGUE WAS THE REAL 'PLAYER' FOR THIS EVENT.