Just as a reference , post 3 in this thread is how I tested my light switch. I saved this picture on my PC just to have a reference to how the switch should behave.
https://forums.pelicanparts.com/porsche-911-technical-forum/1013955-need-headlight-switch-help.html
Mine checked out fine except for a few dead spots in the dimmer for the interior lights. Since I replaced them with LEDs I don't use the dimmer very often, they are onw minimum and still give ample illumination.
Also, I consider the following updates a necessity to the light circuit :
- headlight / high beam relays (don't run the power through the switch)
- fuse (3A) the interior light circuit / ashtray light ! Really - don't leave this unfused !
Other electrical changes done on my 85 Carrera for safety: footwell blower fuses (2x 10A), AC evap blower relay fused (15A), AC front condersor blower fused (7.5A).