Light Control Rheostat
Remove light control rheostat. See Figure. Connect ohmmeter between rheostat terminals. Turn rheostat knob to maximum dark (counterclockwise). Resistance should be 5.1 ohms. Gradually turn rheostat knob from dark side to bright side (clockwise). Resistance should decrease from 5.1 ohms to zero ohms. See Fig 1. If resistance is not as specified, replace light control rheostat.