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Why Doesn’t My External Monitor Work?

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I’ve connected my Optiquest monitor to my HP PC but it won’t restart. I get an RGB “no input” message. What can I do?

This is actually an example question. I get a number of questions like this from time to time. The scenario is this: you have something like a laptop whose screen has failed. In other words, you can’t see what’s on your computer. One of the very common approaches to try and work around that until it gets fixed or replaced is to connect to an external monitor. The problem is that the external monitor doesn’t show anything.

There are a couple of additional steps that might be necessary, beyond just plugging in the monitor.

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Turning on the port

In general, that external monitor port is usually not turned on. You actually have to take extra steps to turn it on.

Normally, on older computers, there was a magical key sequence, usually involving a function key or a manufacturer specific “Fn” key and one of the other keys on the keyboard. I can’t even tell you what it would be because it varies from one manufacturer to another.

On my older Dells, it was a blue “Fn” key used with a key that had a little blue diagram of a monitor on it. By pressing those, it would cycle through the different ways that an external monitor could be used:

  • laptop monitor only
  • laptop mirrored to the external monitor
  • the external monitor only so that the laptop screen was turned off

By cycling through each one of those, you could get the external monitor to do whatever it is you wanted the external monitor to do.

External MonitorOne of the complications is that it often took something like five, or even ten seconds, of being in one of those states for either the computer or the monitor to figure out that it had been turned on, that it had been connected and it should show something.

So one of the things to do is to look on your computer for some special key sequence that causes it to act as I described; that causes it somehow to either enable or cycle through the various ways that the external monitor can be used. You may need to check the documentation for your machine to find out exactly what that keystroke is.

Windows 7 adds support

Now, what’s really kind of nifty is that Windows 7 actually incorporated native support for this kind of thing. Holding down the Windows key and pressing the letter “P” invokes what’s called “Projector mode.”

Normally, on a working machine, the assumption is you can see what’s on the laptop screen – and if you do that on your laptop, what you will see is a pop-up where you can choose how you want that external monitor to be used:

  • external only, laptop screen off
  • external mirroring what’s on the laptop screen
  • laptop screen only, external monitor off
  • laptop screen and external monitor combined as a two monitors system

The problem of course is what happens when you can’t see the laptop screen because the laptop screen is broken.

I believe that if you press Windows+P repeatedly, it will cycle through the various options. Now, again, I have to caution you that you should do so slowly. Give the external monitor a couple of seconds to figure out that somebody’s trying to talk to it, that the laptop is trying to send it a signal.

Depending on the hardware that’s involved, both the laptop and the monitor itself, it can take a few seconds for them to figure it all out. Once they do, then you’re done and you can see what you’re up to.

But that’s the kind of a thing that I believe you’ll need to go through to actually get your external monitor to work if you can’t see the laptop screen.

17 comments on “Why Doesn’t My External Monitor Work?”

  1. From my experience using projectors and an external monitor with Windows 7 & 8, simply plugging the projector into the VGA port causes the computer to output a cloned image of the screen to the external device. I don’t know if that’s true in all cases, as I use fairly a new monitor and projectors. Older monitors may not be plug and play.

    • I don’t think it’s a function of the monitor at all – particularly not for those connected via VGA. This has to do with the computer it’s being connected to, and my experience is the exact oppposite: no display at all until you fiddle with something. Other connection types (HDMI, DisplayPort, USB) are more likely to behave as you describe, because they were designed from day one to be bi-directional and tell the computer “I’m Here!”. VGA not so much.

      • Then what must be happening is that the first time I plugged my computer into a projector or external monitor, Windows remembered what I told it the first time.
        But when I unplug my external monitor from my laptop, the laptop monitor turns on, and when I plug it back in again, the laptop monitor turns off again. So there is some kind of detection going on.

  2. Hi i have a laptop (MSI VR602) and an external monitor Samsung SM5230. I want to connect this external monitor to the laptop. I plug in the cable, then the “no signal” message turns off, instead of that message, after i plugged in the cable i see a black screen and the little light from monitor keeps blinking. I tried with the Fn key and with the right-click and choosing monitor from there. (i forgot, i have win7). When i go right-click->screen resolution i have there the “SM5230” but when i click on it the resolution selection becomes invisible and i can’t choose resolution from there. I forgot to tell you that before windows load the monitor works perfectly. i can see the MSI logo, i can enter the BIOS and all with external monitor, but after the windows load a bit at “Starting windows” black screen it turns off with blinking light. (i installed the windows many times, no result). Can you help me please?

  3. Andrei…i have the same problem too…but i get round it by windows button + P and keep changing it from external to duplicate screens and eventually my monitor switches on!!…its like rebooting the external screen so many times till it finally boots the right requirements to display from the computer!!!

  4. My external monitor quit working in the middle of watching a video using Google Chrome. The video (and sound) just cut over to the laptop screen, leaving still from the video on the external monitor. I have tried switching the monitor off and on, unplugging and replugging the VGA connection and rebooting the laptop. When I attempt to extend the laptop to the external monitor, Windows 7 can’t see it – it only sees the laptop monitor. I have a nice wallpaper (the video still) on the external monitor, but nothing else. Any ideas?

    The laptop is a Dell Latitude E6530 running Windows 7 Professional connected through a Dell docking station to a Dell monitor which worked until earlier today. The problem appears to be at the laptop end probably in Windows, but that’s just my guess.

    • You said that you tried to extend the laptop display to the external monitor. That might be the problem. When setting up the external monitor the setting should be duplicate or clone, not extend.

  5. help!
    I’ve connected my external monitor (which works 100%) via VGA and the screen turns on for about a second, then turns off again (monitor is still on). Then as andrei stated, the power light blinks. I have tried sasian’s solution but to no avail. HELP!!

    • I have a similar problem as G. The external monitor displays the desktop for a second and then goes black. My power light does not flash. HELP!

  6. I am chronologically aged and not a techie in any way, shape or form, but still trying. With info from this site I have just hooked my Dell monitor E173FPb up to my Toshiba laptop. The Toshiba uses windows 7. I wish to use the external screen in conjunction with my lap top when doing my genealogy research (diferent screens on each monitor). The monitor, at first, mirrored the laptop. After doing the ctrl/F5 I feel as though the monitor is set for two screens, different info, and the screen was black so I did the window key +P and the window blinked for a while and then when I released the window/P keys, the picture from my desk top popped onto the external monitor. I feel that I am halfway there but now I need to know how to use the screens separately. At one point I read to right click on an open spot on the screen and click on screen configuration (I believe) but when I right clicked, it had other info such as print, back, forward, etc. but nothing saying screen anything. So, now I am stuck. How do I use the lap top key board and have one open window on the lap top screen and then switch over to the external monitor and show an entirely different screen.
    Thanks for any detailed help.
    Not a Techie!

  7. Hi, I have an Asus UX31E laptop, and I’m trying to connect it to an LG monitor via a HDMI cable connected to the laptop’s micro-HDMI port via an adaptor. The monitor works fine, and detects the laptop, but the laptop doesn’t seem to reciprocate. I’ve tried numerous times to detect the monitor from the laptop to no avail, having tried the fn+f8 and windows key+P options, as well as manually through control panel. Do you have any idea what else I could try to get it to work? Thanks!

  8. Hello!
    I have recently been dual screening my laptop to my monitor so i can watch Netflix while i do work.
    However last night i plugged in my HDMI and my monitor screen just stayed black & and i cannot see/use any windows on my laptop?
    not sure what has happened any help would be appreciated!

    Windows 8.1 a Dell inspiron 17 5000 series laptop

    • Sounds like the screen selection has changed. Try the suggestions in this article under “Turning on the port”.

      • Hi Connie, when my monitor is plugged in goes black with a little bit of flicker of trying to light. However my laptop is not usable when it is plugged in, the windows won’t show (because i assume they are being displayed on the other monitor) so i cant access options when its plugged in. Fn+F8 has a picture of a dual screen on it. So shall i press then when there are both connected?

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