Hello Everyone
So looking for help to use my Original Microphone(s) on my aftermarket Android Screen. My Head Unit (Command System) is not working/not turning on. The ON button is stuck on flasing. I was told need to replace the whole command system which is expensive and also needs programing which cost $$$ so I went the After Market route. And opened up a new can of worms.

So basically the after market Android Screen I installed gets power and piggy backs off of the Comand System to work 100%.
But since the Command System is not working I having to find alternate ways to get some of the functionality of the Aftermarket Screen. I have been able to get sound from the Original Speakers by using an aftermarket apm and running wires to the speakers. I am going to try out using an Optical Decoder like the picture below to get sound out using the Harman Kardon Amplifier.


Optical Decoder


But my issue is the aftermarket screen has a 3.5mm jack for attaching microphone. But this microphone creates an ecoh the caller is able to hear thier own voice as an echo.

I didn't have this issue before using the original microphone. The aftermarket supports using the original microphone but for that the comand system needs to be working.

So I was thinking hardwiring the original Microphones to the aftermarket screen.

Here is the pin out digram for my Head Unit harness.

Pin out diagram.

So here it shows Microphone In, Out and Grounding pins for 2 microphones.

I am trying to make sense on how to hardwire both microphones to the single 3.5mm jack. (Even if that is possible)

Alternatively was thinking that since the After Market screen piggy backs off of the original harness and doesn't need the 3.5mm microphone if the Command Unit is working. Creating a loop from the Mic In + and Mic out - and providing ground would get the Original Microphones working with the aftermarket screen.

Or am I way over my head with this. Please kindly help.

I am not a technical person at all will have professionals do the job. But the tech's I am working with are not familiar with Mercedes Systems so I am doing the theoretical leg work for them.