My external monitor shuts down when I close my MacBook Air

Not sure if you've found a solution but I've had a similar, inconsistent, problem. It seems like the M1 needs more power for the USB-C connections to work than my prior machine. After trying multiple M1 Macs (I sent mine back and tried a new one, and my wife's machine has the same problem, so 3 machines), and multiple USB-C Hubs (Apple, Belkin, & QGeeMe) and multiple chargers (Apple and many others) I've come up with what seems to be a fairly stable solution which is:

Use a genuine Apple Power Adaptor

Other adaptors work *sometimes* or *never*.

The problem seems to be if your Mac doesn't get enough power it shuts down the external display... and a lot of 3rd party chargers are pretty flakey. I've also upgraded from the 61W to the 96W to ensure I always have enough power and it seems to be OK.

Use your Mac notebook computer in closed-display mode with an external display

Learn how to use an external display with your Mac notebook while its built-in display is closed.

You can use an external display or projector with a Mac notebook while its built-in display is closed. This is known as closed-clamshell or closed-display mode.

Check requirements

To use closed-display mode with your Mac notebook, here's what you need:

• An AC power adapter or an external display that provides power over USB-C or Thunderbolt 3 (USB-C).
• An external keyboard and mouse or trackpad, either USB or wireless.
• A ➔ USB-C to USB adapter or cable if you're using a USB mouse or keyboard with a ➔ Mac that has USB-C ports.
• An external display or projector.

Enable closed-display mode

1. Connect your USB keyboard or mouse to your Mac or external display, or ➔ pair your Bluetooth keyboard or mouse with your Mac. If you use a Bluetooth keyboard or mouse, choose Apple () menu > System Preferences, click Bluetooth, then verify Bluetooth is on.
2. Connect your Mac to power with the AC power adapter. Some external displays, like the ➔ LG UltraFine 5K, also charge your Mac.
3. Connect your external display or projector to the appropriate port on your Mac. Use an ➔ Apple video adapter if necessary. Some external displays have a USB cable that needs to be connected to your Mac.
4. After your Mac notebook's desktop appears on the external display, close your computer's lid. You might have to press a key or click your mouse to wake the external display.

If your external display or projector doesn't turn on after you connect it to your Mac, connect your display while your Mac is asleep or off, then wake or turn on your Mac.

Axel F.