CLRNC AMENDED ON APCH IN IMC CONDITIONS CREATE AN OVERLOAD SITUATION FOR FLC AND AFTER A HDG TRACK DEV THEY MAKE A MAP.

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WE WERE APCHING DFW AT XX00 AM AFTER AN ALL NIGHT FLT FROM THE W COAST. THE FO WAS FLYING AND WX WAS 200 OVCST AND 32 MI WITH RAIN. HAVING FLOWN INTO DFW FOR YRS I KNEW THE RWY ASSIGNMENT MIGHT COME LATE SO I INQUIRED EARLY SO WE COULD BRIEF AND BE FULLY PREPARED. THIS WAS ABOUT 35 MI OUT AND ABOVE 1000 FT. 18R WAS ASSIGNED AND THOROUGHLY BRIEFED. WE WERE TURNED OVER TO THE FINAL CTLR ABOUT 15 MI OUT AND SURE ENOUGH WE WERE TOLD OUR RWY WAS NOW 17L. LOOKING BACK I REALIZE I SHOULD HAVE REFUSED THE CHANGE. (MADE FOR CONVENIENCE ONLY). THE FO IMMEDIATELY BRIEFED 17L. I REPROGRAMMED THE FM AND XCHKED OUR NEW MINS WHICH WAS PARAMOUNT ON MY MIND. OUR ILS FREQS WERE XCHKED AND WE WERE CLRED FOR THE INTERCEPT. WE SWITCHED FROM MAP TO ARC MODE ON OUR NAV DISPLAY AND SAW THAT WE HAD GONE THROUGH THE FINAL. AGAIN THIS WAS NOT UNCOMMON AT DFW. I ASKED APCH TO CONFIRM. HE SAID NO; WE WERE FINE; I THEN ASKED WHICH RWY HE SHOWED US CLRED FOR (THIS HAS ALSO BEEN CONFUSED BY APCH IN THE PAST) AND HE SAID 17L. I REALIZED THEN THE MISTAKE WAS OURS. BOTH THE FO AND MYSELF WERE POSITIVE THE ILS FREQ HAD BEEN CHANGED AND CONFIRMED; BUT WE WERE BOTH WRONG. THE CTLR ASKED IF WE WANTED 18R BUT I FELT THAT EXCEPT FOR THE FREQ WE WERE PREPARED FOR 17L SO WE PROCEEDED. I ASKED AND WAS APPROVED FOR A LOWER ALT BECAUSE WE WERE PUSHING THE MARKER. FEELING WE WERE CLOSE TO THE LOC AND IN CLOSE WE DSNDED RAPIDLY. WE PAST OUR CLRED ALT; WERE INSIDE THE MARKER NOW AND THE LOC HADN'T MOVED SO I TOLD THE FO TO GAR. THIS PROBLEM IS FRUSTRATING BECAUSE LAST MIN RWY CHANGES HAPPEN FREQUENTLY AND ARE DANGEROUS. OUR MISTAKES WOULD HAVE BEEN MINIMIZED OR NON EXISTENT IF NO RWY CHANGES WERE ISSUED BELOW 10000 FT WHEN THE FIELD IN IFR (ESPECIALLY AT XXOO AM) UNLESS OPERATIONALLY REQUIRED OR UNLESS THE CREW REQUESTS IT. I WILL SEEK THIS POLICY CHANGE THROUGH MY COMPANY.