Computer Turns On and the Fans Spin, but There's No Display: What's Wrong?

The computer seems to turn on: lights come on, fans spin up, and sometimes you can even hear the drive start. But the monitor stays black or reports "No signal". It's baffling — the computer is clearly alive, yet you can't use it. This is one of the most frequent faults people call us about, and it has many possible causes, from trivial issues that take a minute to fix to a failed motherboard.

Why a computer that's "alive" may show no picture

Spinning fans tell you only one thing: the power supply is delivering voltage on at least some of its rails. It doesn't mean the processor has started, the memory has initialised or the graphics card has come on. Fans start spinning before the motherboard has even checked the components. If something fails during the self-test, start-up halts and never gets as far as sending a picture to the screen.

So the key diagnostic question is where exactly start-up stopped: the computer isn't starting at all, it starts but can't initialise the video, or everything works and the problem lies with the monitor and cable.

The most common causes

Monitor, cable and port

It's worth starting with the simple things, and a technician does exactly that. The monitor may be set to the wrong input (HDMI 1 instead of DisplayPort), the cable may be damaged, or it may be plugged into the motherboard's built-in video output when a separate graphics card is installed. In that case the built-in video is disabled and the monitor is quite right to say there's no signal. This happens surprisingly often — after cleaning or moving house, for example.

Memory

Oxidised contacts, a module that has worked slightly loose or a faulty stick all halt start-up at the earliest stage. Often such a computer gives no beeps at all, because modern cases don't include a speaker.

The graphics card

A graphics card needs auxiliary power from the PSU; if that connector has come loose or the power supply is too weak, the card won't start. GPUs also suffer from heat over time: the solder under the chip can crack, and the card stops producing a picture even though its fans keep spinning.

Reset or corrupted BIOS settings

After a failed BIOS update, overclocking or a dead CMOS battery, the board can hang at start-up. Sometimes a proper settings reset helps; sometimes the firmware has to be restored.

The power supply

A PSU can power the fans yet fail to deliver stable power to the processor or graphics card. Faults like this aren't visible and can only be found with a tester under load.

Processor and motherboard

Swollen capacitors, burnt components in the CPU power circuit and damaged socket contacts are the most serious possibilities. They often appear after power surges and thunderstorms.

Clues the computer gives you

• beep codes — if a speaker is fitted, a pattern of long and short beeps points to memory or video;
• diagnostic LEDs on the board labelled CPU, DRAM, VGA and BOOT — the lit one shows where start-up stopped;
• the Caps Lock light — if it won't toggle, the system most likely hasn't started at all;
• fan behaviour — fans that ramp to full speed and stay there are another sign of an early halt;
• restarting every few seconds — often a memory or power problem.

What not to do

The most common mistake is opening the computer and moving parts around at random. Without experience it's easy to break memory slot clips, bend CPU socket pins or cause a static discharge that finishes off a part that was still working. Buying a new graphics card on a hunch does just as much harm: if the problem is the memory or motherboard, the money is wasted — and the old card may have been fine all along.

How a technician finds the cause

1. Rules out the monitor and cable by connecting a known-good monitor and checking the correct video output.
2. Checks the power by measuring the PSU's voltages under load.
3. Reads diagnostic codes from the board's LEDs or a dedicated POST card.
4. Works with a minimal configuration — processor, one memory module and built-in or test video.
5. Swaps in known-good components from the mobile kit to pinpoint the culprit.
6. Fixes the fault — from reseating parts and cleaning contacts to replacing a component or restoring the BIOS.

Cost and timing

If the cause is a cable, monitor settings or a memory contact, it's fixed on site in 15–30 minutes. Replacing a power supply or memory module from the technician's kit takes about an hour. Graphics card or motherboard repairs need the workshop and usually take 1–3 days. We give you the exact price after diagnosis and before any work starts.

Need help?

If the screen stays black and you don't want to risk your components, call a technician. We come to any district of Tbilisi and the suburbs with a kit of test parts and find the cause on the spot. Find out more on our "Computer won't turn on" and component replacement pages.