Dash and Instrument lights 83 240D

[83Tank]

I have replaced the reostat control for the brightness of the dash and switch lights. I read someone just bypassed the switch so you can't dim the lights.....who cares.
has anyone done this and can tell me how to? All switches,and dash bulbs are good.
Also, rear defrost button will not stay on. It's new but won't remain in the engaged position.