replace that one too..it worth a ****...when i got my 89 last yr the blinkers were all messed up...i replaced the one under the coulum and it fixed it...the one in the fuse box it for hazards i believe do those work?
i had similar problem. turned out to be a loose connection at the ignition switch. i had blinkers with the key in the "on" postion, but none in the "run". i have an 86 vert. don't know if they are the same
there is a TSB on the ignition switch, its a recall os if its burned and you dont see the TSB safety recall sticker some place there take it to Ford for them to install it.