Light Control Rheostat
Remove rheostat. See LIGHT CONTROL RHEOSTAT under REMOVAL & INSTALLATION. Using jumper wires, connect battery positive voltage to terminal No. 1 and battery negative to terminal No. 3. See Fig 1. Measure voltage between rheostat terminals No. 2 and 3. Voltage should change as rheostat knob is turned. If voltage does not change, replace light control rheostat.