There is a relay, but the most common problem is within the switch. Usually you can verify switch fault by pushing on the knob. If the lights come on, the switch is bad. To remove, pull off the knob, grab the spindle with pliers and pull. Sometimes the back part of the switch will seperate from the housing, if this happens, just fish the remainder out with needle nose pliers. Then unplug the harness and conect to new switch and press in to place.