My blinker and brake light quit on the passenger rear. I put in new bulbs that I know work and still nothing. Changed out the flasher also. It has the running light when you have the headlights on. Anyone have any ideas where I should start to look for the problem.

 

Get a test light or a voltmeter and get somebody to press the brake while you poke through the insulation of the wire at the tailamp. It will be orange/light blue or light green/orange. If you don't have 12v, go up to the steering column and find the same color wire. Test it here. If nothing still, I would suspect the turn signal switch. Wiggle the arm while holding the brake, and see if the light tries to come on.

 

There are no "side blinkers" on an 84 Bronco just marker lights. Check the ground on both sides behind the lights. Check the harness under the truck by the gas tank. These are known corrosion areas. I agree you should also use a test light the check if you have current in the wires. 90 percent of Bronco taillight problems are ground and corrosion related.

 

I once had a problem like this, not on a Bronco, but the problem was with the bulbs. I bought cheap replacement bulbs and had all kinds of problems. I went and got some quality name brand bulbs and all the problems disappeared. Worth checking out...