Dash / Instrument Lights Problem Unresolved Options

[JimVG]

I have researched this problem on this site, and I still cannot correct the issue of no dash/instrument lights on a 1973 914.

The Problem
When key is ON, and the headlight switch is in the ON position none of the instrument light bulbs illuminate. Turning the headlight switch dimmer has no effect. All fuses tested functional.

Testing Procedure
Using a test light that is properly grounded with the headlight switch ON and the dimmer turned to HIGH:
There is no power to headlight switch terminal 58a or 58b (Fuse #7 is functional).
Using a separate test wire with a working bulb connected to headlight switch terminal 58b and the opposite end plugged into an instrument bulb socket the bulb does not illuminate.
Using the same test wire connected to terminal headlight switch 56k (empty and has power) plugged into the same instrument bulb socket the bulb does illuminate (dimmer not functional).

Please advise.

Your time and consideration is appreciated!