Abstract: A rotary thumbwheel switch assembly has a switch module including a translucent light ring for indicating positions of the rotary thumbwheel. The ring is illuminated from within by a light emitting diode which can be snap-mounted in place in the center of the translucent ring. The switch module comprises a thumbwheel to which contact brush sets can be easily secured by a spring biased tab. The switch module can be combined with a separable bezel. The switch module can be mounted from either side of a front panel, and can be connected to circuit assemblies housed by the panel prior to the insertion of the bezel. The bezel secures the switch modules to each other and to the panel. A kit comprising the separable elements of the illuminating diode, the bezel and the switch modules is described. A method for installing the separable elements includes the steps of inserting the modules from the front of the housing panel for testing each module's connection with circuit assemblies prior to installing the bezel.