Chicken lights, can it run off the clearance wiriing?

Look up the wiring diagrams for your truck on google. That jumper is part of the wiring so that either the headlights and the clearance lights will also light the rear tail lights. You can jumper the chicken lights to that circuit but if using incandescent lights, you can easily overload the switch. Using LEDs is not a concern since they pull so little current. I bought LEd replacement bulbs for mine and cut the current way back.

If overloaded the switch could have gone bad. Disconnect the wires and test it with a voltmeter.

 

Wire the chicken lights separate with their own switch. Never a good plan to combine unnecessary lights with required lights.
My 97 has 5 spare circuits (switched and unswitched). Check to see if your 94 has them too.

 

If it's anything like my Mack, those 2 powered wires going to the switch are 2 separate circuits. One has a 15A breaker (marker lights) and the other is on a 20A breaker (headlights).

As others have said, it's generally a good idea to keep "required" lighting separate from "auxiliary" lighting. During a DOT inspection, the "required" lights must work. No need to even turn on the chicken lights, because as "auxiliary" lights they are NOT required and therefore are NOT required to work. That and any time you splice into a wiring, you open it up to problems (corrosion, etc) down the road. Problems with DOT-required lights can get you pulled over, written up, and CSA points to your company.