Help me diagnose why the co-pilot passenger headset jack sounds so faint when engine is running

[Datadriver]

4 place intercom, garmin GMA345 audio panel. Of the 4 sets of jacks, all work as expected except the copilot jacks. The microphone jack always works, but the headset jack(listen) produces very little volume at all once
the engine is running. Adjusting the volume control on the 345 works as expected if engine not running or if you are using the 2 backseat jacks but seems to do nothing to raise the volume on the copilot jack. Problem
goes away when engine is not running.

Problem surfaced after big avionics upgrade when the 345 was installed and they replaced the front seat jacks.

Is there supposed to be some sort of filter on that jack? It is 100% consistent with the problem. The other 3 stations are fine, engine running or no.

Problem can be recreated with different headsets on the copilot side, so it is not the headset itself.

 

[Bell206]

Problem surfaced after big avionics upgrade when the 345 was installed and they replaced the front seat jacks.

Still under warranty? If so take it back.

Try unplugging the other 3 headsets and only plug in at the suspect jacks with a headset and see if the same. Possibly a RF/EMI issue since it needs the engine, ie., alt or gen on line.

 

[asicer]

Swap in a known-good GMA345 compatible unit?

 

[Tarrow]

That could be a single point ground or shielding issue. See section 2.10 of the installation manual. Still something that the installer needs to fix, not you. https://static.garmin.com/pumac/190-01878-02_06.pdf

 

[Dan Thomas]

4 place intercom, garmin GMA345 audio panel. Of the 4 sets of jacks, all work as expected except the copilot jacks. The microphone jack always works, but the headset jack(listen) produces very little volume at all once
the engine is running. Adjusting the volume control on the 345 works as expected if engine not running or if you are using the 2 backseat jacks but seems to do nothing to raise the volume on the copilot jack. Problem
goes away when engine is not running.

Problem surfaced after big avionics upgrade when the 345 was installed and they replaced the front seat jacks.

Is there supposed to be some sort of filter on that jack? It is 100% consistent with the problem. The other 3 stations are fine, engine running or no.

Problem can be recreated with different headsets on the copilot side, so it is not the headset itself.

Sounds to me like that jack isn't insulated from the airframe, and stray alternator ground currents are flowing into the audio from ground via the headset, opposing the audio flow.

It's a long shot, but those jacks should be insulated from the panel anyway, and the jack ground run back to the radio rack.

 

[Datadriver]

Still under warranty? If so take it back.

Try unplugging the other 3 headsets and only plug in at the suspect jacks with a headset and see if the same. Possibly a RF/EMI issue since it needs the engine, ie., alt or gen on line.

It's been back 4 times already under warranty for other issues (sigh).

 

[Dave Palacios]

4 place intercom, garmin GMA345 audio panel. Of the 4 sets of jacks, all work as expected except the copilot jacks. The microphone jack always works, but the headset jack(listen) produces very little volume at all once
the engine is running. Adjusting the volume control on the 345 works as expected if engine not running or if you are using the 2 backseat jacks but seems to do nothing to raise the volume on the copilot jack. Problem
goes away when engine is not running.

Problem surfaced after big avionics upgrade when the 345 was installed and they replaced the front seat jacks.

Is there supposed to be some sort of filter on that jack? It is 100% consistent with the problem. The other 3 stations are fine, engine running or no.

Problem can be recreated with different headsets on the copilot side, so it is not the headset itself.

Not an avionics tech, but if the problem occurred after install, thats the place to look, take it back to the avionics shop. Not uncommon to need adjustments after avionics installs especially if a lot of work is done, just the nature of the beast.