help? suggestions?,

I have a new electrical gremlin:  recently my speedo and tach lights
have started to go out intermittently.
I have had the ignition switch replaced in the last year so I don't
suspect that as the culprit.   I also have two light switches so I
exchanged them this afternoon to see if that was the cause ; no luck.
While I had the cover off the instrument housing I manipulated
everything I could identify as related to the lights to see if I could
reveal a bad connection ; no luck.   I wiggled the ignition switch ; no
luck.

I'm stumped.
anyone been down this road already?

John McLean  87 Vanagon GL   (199,000 miles)