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Garmin 340 audio control panel back lighting

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my Garmin 340 is not hooked up to my overhead lighting rheostat. 

Is there a way to get the nomenclature brighter.  It is too dim now.

This was in the manual and I see no other way.  Any hack to this?


Screen Shot 2021-02-23 at 3.10.06 PM.png

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I'm afraid there is no "easy" adjustment of the nomenclature lighting; the only way to get them to a brighter level is to input a higher voltage at J2 Connector, Pins #6 and 7, ideally controlled via the lighting rheostat. Assuming your M20C uses a 14V system, when 0 volts is applied to J2 pins 6 & 7, then nomenclature lighting is off, but at 12 volts, nomenclature lighting is a full intensity.

I'm not sure what exactly your J2 Pins 6 & 7 are connected to, but I have noticed not many avionics installers out there are thoroughly diligent with regards to properly hooking up the avionics to their respective lighting busses, so there may be a chance that your pins are connected to system voltage with a series load resistor (to drop the voltage down to something like 5V) or not connected at all.


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If looking for the source of dimmed voltage...

There is a node(?) near the pilot’s yoke in the vicinity of the lightbulb that lights up the fuel selector valve...

All the instrument lights that get dimmed are connected there...

Find the bolt with a half dozen ring terminals going to it...

PP thoughts only, not a mechanic...

Best regards,


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