2000 Ford Ranger dash area clicking

2000 4.0L 4x4 Ford Ranger, Has a clicking noise which sounds like contacts making and breaking repeatedly only when vehicle is traveling down the road. The noise seems to come from the area to the right side of the steering wheel under the dash at the bottom, cause the noise is very easy to hear not muffled. I cannot find anything that is operating intermittently during the clicking events. Very difficult to locate problem under dash while driving down the road at the same time.