Internal Speakers not present only Headphones

Hello Team,

I have a very frustrating issue.

A customer has come to my shop with a this Macbook air for the internal sound not working.

First of all I noticed that the "Alt Sound Option" was only showing Headphones, when none were plugged in.

So I replaced the IO board and data flex connecting it to the main board, no change to issue.

Then I used a USB drive with a known good copy of OSX on it, no change to issue

Next I replaced the logic board, no change to issue.

Next I removed the logic board from the chassis incase there was some kind of short from the casing, I set the logic board and IO board up in my test bay and connected only the required hardware to boot the device.

So the state of play so far is, new logic board, new IO board and flex, no SSD, OSX loaded from external HDD, no wifi board, new internal speakers connected, new fan.

THE ISSUE IS STILL PRESENT.

How can this be possible?

I should note that the start up chime works .

Also when using headphones the sound is really low on both IO boards and logic boards, but when I would use the MIDI setup and mute either channel one or two on the output the sound is at the correct volume on the headphones.

Also note internal speakers do not appear anywhere in the MIDI setup only headphones, even with new parts.

Any Help would let me sleep tonight.

Cheers

Brendan