Garmin GI-106B CDI Internal Lighting Problem

[Van Lanier]

I just installed a GNC355 with GI-106B indicator in a 1963 M20C.  The internal lighting is very faint and virtually dark at night, rendering the CDI useless.  The annunciator lights (To-From, etc.) are fine, but the internal LED is not.  The 14V lighting input is attached to Pin 23, as called for in the wiring diagram.  If anyone has any suggestions on how to fix this, I sure would appreciate hearing them.  The avionics shop is at a loss.  Many thanks. 

[glbtrottr]

I am curious a well


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[PT20J]

I would first measure the voltage at pin 23.