I have a ThinkPad X230 running Linux Mint Cinnamon on X11 with Intel integrated graphics. The external VGA monitor appears in Display settings and xrandr, but it says no signal. Both extended and mirrored layouts behave the same way, and xrandr --auto and Fn+F7 have not helped.
The cable and monitor work, and I can even move windows onto the external display, though I cannot see them. What should I check next?
Start by checking what X11 is actually sending to the VGA output. Run xrandr --verbose and find the connected VGA output, its current mode, refresh rate and position. The output name might be something like VGA-1, but use the exact name shown on your machine.
Then try enabling a mode listed for that output explicitly, for example xrandr --output VGA-1 --mode 1024x768 --rate 60 --right-of eDP-1. Replace both output names and the mode with ones from your xrandr output. A modest resolution and 60 Hz are useful for testing if the monitor reports that mode. If the command errors, include the error and the full xrandr output.
Check the monitor's input menu and make sure it is set to VGA, even if the cable and monitor work elsewhere. Also try a full shutdown, connect the cable, turn the monitor on, and then boot the laptop. That can help distinguish a connection or startup issue from a layout setting.
The desktop treating the monitor as usable does not prove that the physical VGA signal is getting through. Since the cable and monitor have been checked, the laptop's VGA socket or output could still be involved. If available, test the laptop with another VGA display or test another operating system on the same hardware before blaming the port.
If the basic checks don't change anything, try an older kernel from the boot menu, if one is installed. The reported kernel is another variable worth testing. Include the results from xrandr --verbose and any graphics-related errors in the system log when asking for more help, rather than assuming the driver is the cause.
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r918!foldmode_2:
If a lower mode works, try the monitor's preferred resolution next. Detection alone does not confirm that the chosen signal is one the display will accept.