Second monitor keeps turning off: how to fix it

These steps are the same on Windows and Mac. Change one thing, then wait long enough to know whether it helped.

1. 1

   Step 1 · Swap the cable

   Next up

   Use a known-good cable. If you can, try the other port type, such as HDMI in place of DisplayPort.

2. 2

   Step 2 · Connect the monitor directly

   Plug the monitor straight into the computer, without the dock, adapter or daisy chain.

3. 3

   Step 3 · Turn off the monitor's power saving

   Monitor menu › Power saving, Eco or Auto power-off

   Turn off power saving, eco mode and any auto power-off timer. Names differ by maker.

4. 4

   Step 4 · Set the input to your port

   Monitor menu › Input

   Choose the port you use, not automatic. An automatic input scans for a signal and sleeps when it finds none, and fixing it often cures "No signal" after wake.

5. 5

   Step 5 · Update the graphics driver

   Settings › Windows Update › Advanced options › Optional updates

   An old driver can mishandle sleep and wake on external screens. On Windows, check here or the website of your PC or graphics card maker. On a Mac, drivers come with macOS updates.

If the menu will not open or ignores changes, some monitors have a menu lock; the manual says how to release it.

If the screen still goes dark

1. Start AwakeTab and wait for “Screen awake”.
2. On Windows, run powercfg /requests in an administrator terminal and look for the browser under DISPLAY. On a Mac, run pmset -g assertions and look for a NoDisplaySleep entry.
3. If the request is there and the second screen still goes dark, the timeout is not the cause. Go back to the cable and monitor steps.

Which pattern do you have?

• Only the second screen goes dark, at random times: the cable, adapter or link.
• Only the second screen goes dark, after a steady delay: the monitor’s own auto-off or eco timer.
• The second screen shows “No signal” after the computer wakes: DisplayPort re-detection or the monitor’s automatic input search.
• Both screens go dark together: the system display timeout.

DisplayPort connections can drop and reconnect, more often through docks or when monitors are daisy-chained (MST). A monitor that drops the link can look unplugged to the computer for a moment.

When both screens go dark together

Windows and macOS use one display timeout for all screens. To change it:

• Windows 11: open Settings > System > Power & battery and expand the screen, sleep and hibernate timeouts.
• Mac: System Settings > Lock Screen, then the two “Turn display off” choices.

On a work computer these may be greyed out because IT sets them. In that case, leave them as they are.

Where to put the AwakeTab tab

Put it where nothing covers it. A tab in a minimised window counts as hidden, and one fully covered by another window can too; the pill then shows “Paused — tab hidden”. A window that is visible but not focused is fine.

For a wall screen running all day, see keeping a dashboard screen on. If you present from a laptop onto the second screen, see presenting with AwakeTab. Browser setup for each system is on the Windows 11 page and the Mac page.