[Bob Kontak]

My 81 Owners manual states that the switch knobs only illuminate when the circuit is energized.

Here is something I just learned and I bet (hope) you have your knobs confused, The defogger function is engaged by pulling the knob and the mirror defroster is engaged by turning the knob to the right. Either of these will kick in the defrost switch light.

Fog lights only work when knob pulled and only when low beams are on.

Did not see mention of two pull steps for either knob.