Fixed mortgage rates in the U.S. fell to a record low for the second consecutive week, Freddie Mac (FRE) announced Thursday, a sign that Federal Reserve Chairman Ben Bernanke’s recent move to spur the housing market is working.

The 30-year rate dropped to 4.78% from 4.85% a week earlier. The current rate represents the lowest in Freddie Mac’s records dating back nearly four decades.

The average rate on a 15-year fixed mortgage also hit a record low of 4.52%, down from 4.58% a week ago, the McLean, Virginia-based Freddie Mac said.

“This is exactly what the Fed is trying to do,” said Gus Faucher, director of macroeconomics at Moody’s Economy.com.

Rates are falling following the Fed’s announcement on March 18 that it would step up purchases of mortgage-backed bonds to support home lending. The Fed said it would buy up to an additional $750 billion of mortgage-backed securities.

The Fed’s efforts to expand lending “should make new consumer, business, and mortgage loans more available, at lower cost,” Bernanke said in a March 20 speech to a Phoenix banking conference.

As a result of the Fed’s efforts to jump start the housing market, mortgage applications in the U.S. rose for a fourth consecutive week as a decline in borrowing costs prompted more refinancing.

Faucher said lower interest rates and more home buying were the hoped-for results of the Fed’s action.

Rising default rates had all but shut down the secondary market for mortgages, making many banks leery of approving the loans. But if banks know there is a market for their mortgages, they will be more likely to lower interest rates in an effort to attract borrowers.

The Fed took care of that by creating a market for the loans.

And with rates falling to historic lows, more consumers have been testing the housing market waters.

The number of Americans signing contracts to buy previously owned homes rose 2.1% in February, the National Association of Realtors said yesterday.

And the refinancing market has been especially robust since the Fed’s announcement.

Faucher said the increase in refinancings is helpful to the broader economy because “it puts more money in peoples’ pockets.”

Meanwhile, homebuilding stocks rallied 25% in March on speculation that lower interest rates will lead buyers back into the market.

Los Angeles-based KB Home rose 61%, the most of any builder, last month after saying orders increased for the first time in three years. Chief Executive Officer Jeffrey Mezger has said the company’s net orders will likely rise for the rest of the year.