Air has black screen except for a thin band across the top

I didn't mention initially that if I bring the cursor to the thin band that shows, you can see the tip of the cursor.

Moving the screen does not change anything when it is malfunctioning or normal.

I have not started a dissection yet, as I wanted to get a sense of where to head before jumping in.

I have not tried an external display, which would greatly help to differentiate the problem.

I will do these tests tomorrow and see what they show. Thank you for the suggestions.

@jmccorison - Let’s see what your testing tells us.

Of the gazillion cables and adapters I have, I don't have one to connect an HDMI display to USB-C/Thunderbolt. One has been ordered, and I will update this post after it has arrived and I've done the test.

Sometimes, life gets in the way... Between caring for an aging parent, everybody getting The Crud, and needing an adapter, this project fell by the wayside. But I'm back at it now.

Connecting an external monitor: With the lid closed, the external monitor takes over as the primary, and everything looks good. Opening the lid shows the internal screen black with the thin line at the top.

I removed the back cover, which immediately resolved the problem. Pressing on the T-CON board and connectors did not cause it to malfunction. Inside the back lip, there was dirt and slight evidence of liquid. I cleaned everything and replaced the back cover, and it continued to work properly. I doubt that is the resolution, but we'll see.

@jmccorison - it that was it you are very lucky!