how do i fix my fuse?

ok, i have a 1994 ford taurus. the 15 amp fuse blows every time i shifT from parK into drive. sitting in park it dont blow. what is the problem ?i have replaced all the blubs.the hazzard lights work fin, the running lights work fine,brake lights are fin. when the fuse blows, the rear defoster,blinkers and reservse lights not work.
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