I have a 260z, and when I use the brakes it will blow the fuse or ture on the flasher it will blow the fuse what could this be ?

Is the car new (to you) or is this something that just started happening? Did you recently change or replace the brake light bulbs? Without knowing the history, all I can say is that it sounds like you have a short in the brake light system somewhere (I think you already knew that!) and about all you can do is track through the circuit until you find it. Remove one brake light bulb and then try it and then the other if that doesn't work. Make sure you have dual filament, dual contact bulbs in those sockets and that the sockets themselves are in good condition. That will confirm or elminate the bulbs/sockets as the problem.

The car is fixed now I found where a shop did a hack job so I had to fix it wright .

Thanks