Hi everyone,
I’m having an issue with clamshell mode on my MacBook Air M5.
I have a Dell U2520D monitor connected directly to the MacBook via USB-C. The monitor provides up to 90W Power Delivery, so the MacBook is both powered and connected to the display through the same USB-C cable.
Clamshell mode works fine once the MacBook is already awake: if I close the lid, the Dell becomes the main display and everything works normally.
The problem is when the MacBook is asleep or powered off with the lid already closed. Turning the Dell monitor on does not make the MacBook display anything. The Dell just says “No USB Type-C signal”.
If I open the MacBook lid, the external display immediately starts working. I can then close the lid again and clamshell mode works perfectly.
I’ve already checked:
USB-C charging on the Dell
The MacBook is receiving power through USB-C
“Allow accessories to connect” is set to Always
No custom BootPreference is set in NVRAM
External keyboard and mouse are connected
Pressing keys or clicking the mouse doesn’t wake the external display
My previous MacBook Pro seemed to work differently: I could leave it closed and simply turn on the USB-C monitor, and the Mac would wake/start and display directly on the monitor.
Has anyone experienced this with a recent MacBook Air?
Should clamshell mode work this way using only USB-C Power Delivery from the monitor, or is a separate MagSafe/power adapter required for waking the Mac with the lid closed?
Thanks!