Computer starts up but monitor has no signal

Solved) VGA no signal | Easy guide

I often get requests with this problem. the monitor doesn’t turn on. The computer turns itself on, but the image does not appear on the monitor. After arriving at the place of the call I make diagnostics and after some manipulations, monitor shows again. Let’s check 9 main reasons why the monitor doesn’t turn on when the computer is switched on.

First of all you need to make sure the monitor is connected to the electric mains. To do this check the power cable connection to the monitor. The cable must be tightly seated in the socket on the back of the monitor and in the socket itself. If the LED on the monitor is on, it means that the power is there. the cable is OK.

If there is no power supply it is possible that the cable is burned out. It doesn’t happen often, but it’s possible. Check the cable visually, if you notice some suspicious places of the insulation melt, replace the cable for a new one.

If the outside of the cable is all right, then check the cable for breaks with a multimeter. this is a tester, an electrical measuring device.

For this we put the multimeter in continuity test mode. Insert one probe into the plug contact and connect the other probe to the plug, as shown in the picture below.

Check monitor’s cable with multimeter. no breakage

You need to check two outer wires in the cable. The central component is usually the ground and does not affect the operation. If the multimeter beeps and shows constantly changing digits, it indicates a faulty wire. Also check the second wire in the cable.

Here is what a multimeter will read if there is a break in the cable. I didn’t connect one pin on purpose, it was a simulation of a breakage inside the cable.

Open circuit simulation. multimeter shows an open circuit in the monitor cable

If the tester doesn’t beep and the numbers don’t change on the display it means there is a break in the cable. replace the cable with a new one.

Check your graphics card

If you have a problem with your video card see the following

In most cases the video card is a separate card which is plugged into the corresponding output on the motherboard. If you need a new card you can quickly install a new one.

If your computer has an integrated graphics card you should skip this step. In that case the graphics is processed by a separate motherboard chip and we will talk about that below. The most trivial reason is related to the failure to regularly clean the video card. As a consequence, there is a slight corrosion on the gold contacts.

There are various errors associated with the GPU. For example, the fan of the card stopped working or it needs to be rebolled. So you will have to open the computer case and remove the card.

It is desirable to put on ESD grounding straps before this procedure, and of course the computer must be disconnected from the power supply.

The procedure does not involve anything complicated. the main thing is to have a screwdriver handy. With it you can proceed to the disassembly of the system unit. start with the screws on the side cover. Not superfluous would be to remove all cables from the port and then remove the video card. As a rule, it is installed in the PCI x16 port and a special holder is responsible for its stable position.

After successful removal, you can connect the monitor cable to the port (if there is a built-in card) or install another. If it works, it indicates that the video card is faulty or that you need to clean it. But if your computer still has no video signal, you will have to continue testing.

In 90% of cases it is enough to properly clean the graphics board. This will ensure a proper connection between it and the motherboard, and the video signal will appear. For this case, you need to unscrew the screws that hold the fan on the card and get rid of the dirt with compressed air and similar solutions. Then you need to soak a cotton swab in 99% isopropyl alcohol and proceed with the actual cleaning.

Status of peripherals

Just plug in the RAM module, CPU, cooling fan and SMPS to make the motherboard work. The rest, including the HDD or optical drive, is used to extend the functionality of the PC.

Accordingly, there may be enough devices inside the system unit that are not required for the correct operation of the motherboard. So it is necessary to check how the computer behaves after removing the additional components. The cause may be in the wrong power supply. Of course, all the necessary components must remain.

The procedure can be performed step by step. removing elements one by one. This will also help you determine the faulty element if the video signal appears after disconnecting one of them. In the case if the video does not appear you need to continue.

Try connecting a different monitor

This simple action will help you to understand which device is the problem.

And there are only two options. the monitor (if when you connect another monitor all works well) or the computer (if when you connect another monitor, there is still no signal).

With the first one everything is much easier. you just need to give the device to repair, because it is useless to try to understand it without knowledge of electrical engineering.

But if there is something wrong with your computer you can try to solve the problem yourself. Here’s what you need to do in such a case:

Remove the video card from the system unit and clean it. In the easiest case do it with a brush (clean!) And with a vacuum cleaner. This will remove all the dust from it. You can also take a small piece of absorbent cotton with alcohol and wipe all the contacts.

computer, monitor, signal

If alcohol is used, you need to wait at least a few minutes after cleaning and then return the video card to its place. In this case you could try to use another video card, because it is quite possible that the old one is already faulty and any attempt to do something with it will be fruitless.

Exactly the same procedure should be done with the RAM. It too can get clogged.

So take a vacuum cleaner, a brush, perhaps a cotton swab with alcohol and do a thorough cleaning of this device. Also try to replace the old memory with the new one.

If it works, it’s time to change the RAM. Before that, you can take your old board to a repair shop. it is quite possible that experienced craftsmen can do something with it.

Disconnect the power to the hard drives and the drive. If the image appears, the problem is in the power supply.

computer, monitor, signal

Of course it is better to take another unit and temporarily replace the old one. if it works, this must be the problem.

To disconnect the power supply, you simply need to remove the SATA cable from the corresponding device. It may look like the one shown in Fig.7.

Pay attention to the system unit. If there is no LED blinking (even if you can hear and feel the cooler running or there is something going on inside) contact the service center. This indicates that the problem is in the system unit.

Warning! It is not recommended to attempt to disassemble and diagnose the problem yourself. Often the actions of inexperienced users can lead to the failure of this device.

Roll back any recent changes

In some cases, the monitor stops working after updating some program or the operating system as a whole. Therefore it is necessary to remove all last changes or to restore the system.

The best way to do this is to use the disk with the operating system installed on it. If you have Windows installed on your PC the easiest way to recover is to.

You will need to do the following:

Select to boot from a disc or flash drive in BIOS or UEFI. Suppose we have the OS on a disk and we use the BIOS. Then when the system boots, press the F1 button (depending on the version it could be F1, F4, F11 or Delete). Usually the button to open BIOS is already specified during system boot. Select Boot and click on Boot Device Priority. Put DVD (CD) first.

  • Insert your system disk and reboot the computer.
  • When booting up, select “System Restore”. In the next window select the same option and follow the instructions.

If nothing helps, send your monitor and main unit for repair. Specialists will figure it out.

The video below shows you how to clean the video card from dust:

What to do if there is no signal on your monitor when you turn on your computer. a detailed guide

What to do if there is no signal on your monitor when you turn your computer on. a detailed guide

Wrong signal source selected on your monitor

On monitors that have multiple video inputs, there is a button for switching between signals from these video inputs. This button is usually called “Source” or “Input. If the buttons on your monitor are not labeled, then read the manual.

Try repeatedly pressing this button to switch to the other video input. If you select the wrong video input on your monitor, this should solve the problem and the “No Signal” message will go away.

Trouble connecting the monitor to the computer


If you get a message that there is no signal detected when turning on your monitor then the first thing to check is the cable you use to connect your monitor to your computer. There are usually two problems with the cable: the cable can lose contact where it connects to the computer or monitor, or the cable is faulty and needs to be replaced.

The first thing to do is to check the contact at the cable connection points. To do this disconnect the cable from the monitor and computer and reconnect it. If it is a DVI or VGA cable, be sure to tighten the two screws that fix the cable in the connector.

Breakage of a cable that was working fine before is a rather rare occurrence. But if you have another cable at hand, or you can remove such cable from another computer, you can check how the monitor will work with another cable. Maybe after replacing the cable the problem will be solved.


Another possible cause of problems are adapters. If you connected your monitor through an adapter and you get a “No Signal” error, it is most likely due to the adapter. Such an adapter may not be properly connected or may not be suitable for your current hardware.

For example, DisplayPort to HDMI (DP) adapters only work one way, which means they can convert from DisplayPort to HDMI, but not vice versa. At the same time, if your video card has several DisplayPort video outputs, the DisplayPort-HDMI adapter will only work on the first one.

Passive HDMI to VGA adapters can only work on devices that support analog output over HDMI. This feature is found on DVD players, video cards with this feature most likely do not exist.

A passive HDMI to VGA adapter will only work on some DVD players.

Active HDMI to VGA adapters (with a box) convert the digital signal to analog, so they will work with any video card. But, the conversion is only one way, either from HDMI to VGA or vice versa, depending on the model.

computer, monitor, signal

If possible, try to connect the monitor without using any adapters, maybe it will solve the problem with the lack of signal.

  • Some older graphics cards require drivers to be loaded in order for DisplayPort video outputs to function. In such cases you need to connect the main monitor in another way, otherwise you will not get a picture in the BIOS or when booting from a USB flash drive.
  • Not all USB-C ports on notebook computers can be used for connecting monitors. Some laptops do not support video output via USB-C, and some only on one port. It’s also advisable to use the original USB-C cable that came with the monitor, since not all cables support video transmission.
  • Integrated graphics can be disabled in the BIOS. So if you switched from a discrete graphics card to an integrated one, you will need to enter your BIOS and check your settings.

No signal detected on the monitor no signal when turning on the computer

The phrase on the monitor “No signal detected” indicates that the screen signal is not detected. This can occur because the cable from the computer screen was previously connected to the TV. Try to disconnect the “native” cable and reconnect.

The reason for no signal and “no signal detected” may also be the disabling of integrated video in the BIOS. You need to double-check this in the computer settings.