Directionals Not Working

My 70 Challenger the directionals stopped working, The bake lights work- the flashers work- the taillights work just the directionals don't. I checked the ground by the radiator support its good and I changed the flasher relay under the dash and they still don't work. Could it be the signal switch in the column and is there a way to check it before taking it apart? Isn't there a ground on the fire wall also?
Author: KennyCuda