Does this car have an emergency flasher unit? Does it click when the brake lights flash? Is the flash a steady rythm or various rythm? Will the brake lights work correctly with the ignition switch off?
I would look at the emergency flasher switch and wiring inside and out of the steering colum first. May have two wires touching that are not supose too. And one is only hot when the ignition switch is in the "on" position. If you don't have a emergency flasher or it does not seem to be the problem then check the turnsignal switch and wires for the same problem.