Be careful with that bezel. Replacement bezels nuts are 3 pin. I made my own removal tool from a piece a pipe with holes drilled for roll pins (same idea for windshield wiper tower). A screwdriver can mar the finish on the bezel. Try to tighten the nut first. If it's not loose then the switch may be worn inside. There are several parts. Housing, tumbler, bezel and lamp socket. New repop switch parts are hit-n-miss in my experience so you may have to buy the housing and tumbler to get a combination that works okay. You can purchase a replacement type switch if you are not concerned about originality.
This has been discussed in this forum many times before but a 6 volt system requires 2/0 battery cables minimum. Preferably one made with real copper and not clad material. If you buy a new 6 volt battery and use typical skinny 12 volt cables, don't blame the battery.
