Turn Signal blows brake light/hazard fuse

[kennyakataz]

I have a 1982 C10 Stepside. So I was driving home and turned on my left turn signal. Notice the radio was blinking along with my blinker. Then a pop and smoke! It turned out to be my brake light/hazard fuse. All other lights worked fine except for the brake lights/hazards. Tail lights still come on with head lights.
I was able to recreate the symptoms but only when the truck is in drive. It will not do it while in park. Both sides of the turn signal causes the radio to flicker and the battery voltage meter to dance! HELP PLEASE