That on/off switch tends to burn up inside. The good part is, there are two sets of contacts in the switch: One for the main power and one for the dial light. The dial light is very low current so that side is always in good shape. You can't get that switch any more so I just swap the wires so the main power goes through the same set of contacts the light does. The only issue is, the light has its own power source and that wire connects the head light switch so the dial light comes on only when the headlights are on. Doing the switch I described means the dial light is on any time the radio is on. This is how the Henry J radio and early KF radios work so it's not really a problem but the bulb will burn out a little faster.