1993 Isuzu Trooper blinker

i have replaced all bulbs, the flasher, and the fuse. every time i switch my left blinker on, it blows the fuse after 5 or 6 blinks. the right blinker blows it instantly. with both blinkers there is an electrical sound coming from the steering column. i replaced the 15 amp fuse with a 15 amp fuse. i've tried a heavier fuse and it works a little longer, but it heats up and blows eventually. i wasn't having any problems until i replaced my alternator.