87 toyota pickup tail light fuse goes out
 

hello, i got an 87 toyota single cab 4x4 pickup.
problem: the fuse(15 in the cab on driverside) blows everytime i come to my destination(home or where ever). this fuse controls the turn signels in the back and the gas meter and temperture. also my horn goes off every time i turn the wheel a certain way. does this all relate? and how could i fix this problem?