WASHINGTON – Sept. 23, 2011 – Fixed mortgage rates hovered at record lows for a third straight week. They are likely to fall even further now that the Federal Reserve said it would shuffle its holdings to drive down long-term interest rates. The average rate on the 30-year fixed mortgage was unchanged at 4.09 percent this week, Freddie Mac said Thursday. That’s the lowest rate seen since 1951. The average rate on the 15-year mortgage ticked down to 3.29 percent. Economists say that’s the lowest rate ever for the loan.