Dash/center console popping sound

During cold weather months, between thirty to fifty minutes into my drive to and from work (defroster is on) I get a popping sound from the area of my dashboard/center console area. Does not happen in warmer weather. The popping is rather loud and only happens that one time each trip. Have had it to the Toyota dealership seven times in the last year. When first reported, it was under warranty. The last time they had my vehicle for seven days and disassembled the dashboard and re-assembled it and advised me that they found what they thought was the problem and fixed it. Got my car back yesterday and the problem is not corrected. Am at the point of filing a complaint with Toyota of America. Any insight on what the problem might be?