96 Silverado Blowing Turn Signal Fuse
 

I am hoping that someone can help me troubleshoot this annoying problem.
I have a 96 Silverado 3500 Diesel Dually and it blows the turn signal fuse as soon as engine is started. B/U lights and BTSI is on same fuse. I can turn the key to on position and turn both directionals on all day but as soon as engine is started even without signal on, the fuse blows. Two things I have noticed is that I do not have B/U lights and I can put truck in gear without foot on the brake. So I am leaning in that direction but don't know how to troubleshoot. Already changed turn signal switch.