blown fuse on 2004 BMW 530i

why does my cigarette lighter fuse keep blowing out i have replaced it 3 times.

Asked by for the 2004 BMW 530i
Torque wrench is absolutely correct. But I have seen children drop coins in the cigarette lighter socket and or the lighter socket to fail and short due to after market accessories like GPS and radar detectors.
1 more answer , 1 more comment
You might have a short in the element part of the lighter itself or socket. But I need to ask a question do you use the lighter or are you using the socket to power a cell phone chager, GPS or similar equipment? If so, it might just be a short in the power cord to your equipment. I have seen this problem many times from cell phone car chargers. try a different cord if this is the case.
I use for my gps and cell phone