You are making me do something I have not done in a long time - read my Owners Manual.
The headlight switch knob moves out two positions to turn on the exterior lights. You should get dash lights at either position
The knob also rotates. That rotation controls a reostat or dimmer switch.
The Owner's Manual says rotating the headlight switch all the way counter-clockwise turns on the interior (dome) lights. Rotating the switch all the way clockwise turns off the dashboard lights.
If the reostat in the switch is bad, it will be one reason you will get intermittent lights.The reostat has a bunch of fine wire windings on it. If they are messed up in places, you will get intermittent electrical contact.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
