Causes and solutions when the PC does not start but the fan is spinning

This time, we will explain the causes and solutions when the computer does not start but the fan spins.
When such symptoms occur, there is usually nothing wrong with the power supply, but you should suspect that all other parts are abnormal and isolate the cause.
We recommend investigating the cause in the following order.
1. Disconnect all peripherals and restart
2. Check that the backlight of the laptop monitor is not turned off.
3. For desktop PCs, check the monitor connection
4. For desktop PCs, try removing or replacing the graphics board.
5. Discharge for notebook PCs
6. Initializing BIOS (UEFI) for desktop PCs
7. Inserting/removing and replacing memory
In the following sections, we will explain how to deal with each case.
If the PC does not start and the fan rotates at full throttle
If your computer won't start and the fan is spinning at full throttle, a faulty motherboard or CPU may be the cause.
CPUs rarely have defects, so you will need to reset the motherboard's BIOS (UEFI) or replace the motherboard if the problem does not improve.
Causes and solutions when the PC does not start but the fan is spinning
If your computer won't start but the fan is spinning, the following solutions may help.
● Disconnect all peripherals and restart
● Check that the backlight of the laptop monitor is not turned off.
Disconnect all peripherals and restart
If your computer won't start but the fan spins, disconnecting all peripherals and restarting may solve the problem.
If your computer starts up after removing peripherals, it is best to assume that one of the peripherals is malfunctioning.
Check that the backlight of the laptop monitor is not turned off.
If your laptop won't start but the fan is running, check to see if your monitor's backlight is turned off.
The confirmation and replacement method is as follows.
How to check if the backlight is out
To check if your laptop's backlight is turned off, try connecting your computer to an external monitor and booting it up.
If you can see your computer screen on an external monitor, there is likely a problem with your laptop monitor. The backlight may be burnt out.
How to replace the LCD panel
To replace your laptop's LCD panel, you will need to obtain a replacement panel.
Once you have obtained a replacement panel, follow the steps below to replace it.
[How to replace the LCD panel]
1. Remove the LCD panel hinge cover and remove the screws.
2. Remove the cover.
3. Fold the LCD panel horizontally.
4. Remove the switch and speaker panels. (Be careful not to cut the cable)
5. Remove the screws that secure the LCD panel.
6. Disconnect the LCD panel cable.
7. Replace the LCD panel and put it back together in reverse order.
Checking the desktop PC monitor connection
If your desktop computer won't start but the fan spins, check the monitor connection.
Your monitor may not be securely connected to your computer, so the screen may not be displayed, making it appear as though your computer is not on.
You may also try disconnecting the monitor and reconnecting it.
For desktop PCs, try removing or replacing the graphics board.
If your desktop computer won't start and the fan is spinning, removing or replacing the graphics board may solve the problem.
If your computer has an onboard graphics function, you can check whether the problem is caused by the graphics board by removing the graphics board and checking the operation using only the motherboard's GPU.
If there is no onboard graphics function, the above confirmation method cannot be used. Therefore, if there are no other possible causes, you may want to try replacing the graphics board. There is also an external graphics board, so please try using it.
How to discharge a laptop
If your laptop won't start but the fan is spinning, discharging it may fix the problem.
To discharge your laptop, you can follow the steps below.
[How to discharge a laptop]
1. Turn off your laptop.
2. Disconnect any peripherals or power cords connected to your laptop.
3. Remove the laptop battery from the main unit.
4. Leave it for at least 1 hour.
How to reset the BIOS (UEFI) of a desktop PC (clear CMOS)
If your desktop computer won't start but the fan spins, clearing the CMOS and resetting the BIOS (UEFI) may solve the problem.
[How to clear CMOS]
1. Unplug the power supply unit.
2. Disconnect all cables providing power to the motherboard.
3. Remove the round button battery attached to the motherboard.
4. Short the jumper or land (for about 5 seconds or more) to avoid damaging the motherboard.
5. Restore everything.
Try removing and replacing the memory.
If your computer won't start but the fan spins, removing or replacing the memory may solve the problem.
If the problem is caused by a defective memory or poor contact, try removing and reinserting the memory and checking the contact.
It might be a good idea to check for dirt around the memory and try cleaning it.
If the problem still persists, replacing the memory may allow the BIOS to boot normally and resolve the issue.
What to do if the power turns on but the BIOS (UEFI) does not start and the fan spins
If the power is on but the BIOS (UEFI) does not start and the fan is spinning, there is most likely no problem with the power supply.
Therefore, please try the solutions described in each section above.
If you are still concerned, it would be a good idea to use a tester to check whether there are any abnormalities in the power supply.
A power supply tester, also called a power supply checker, is a device that can be used to check whether the correct voltage is being output from the power connector of your computer.
Power supply testers include the following:
MacLab. PC Power Supply Tester Computer Power Supply Voltage Checker PCI-EXPRESS S-ATA ATX EPS Compatible Easy to Use Instruction Manual Included

What to do if your computer won't start but the fan spins and beeps
There may be times when your computer won't start, but the fan spins or you hear beeps.
In such cases, depending on the manufacturer, you may be able to identify the cause by the way the beep sounds.
Below are some manufacturers' beep sounds and their causes.
Dell beep sounds and causes
● If there is one beep
There may be a problem with the motherboard or BIOS.
It may be possible to repair it by initializing it.
● If there are two beeps
The memory may not be recognized.
Try unplugging the memory and making sure it's firmly connected.
● If there are 3 beeps
There may be a problem with the motherboard or chipset.
There may also be a time clock test failure, Gate A20 error, super I/O chip failure, or keyboard controller problem.
● If there are 4 beeps
There may be a memory problem.
Removing or replacing the memory may solve the problem.
● If there are 5 beeps
There may be a problem with the CMOS battery.
Try removing and reinserting the CMOS battery.
● If there are 6 beeps
There may be a problem with your video card.
● If there are 7 beeps
There may be a problem with the CPU.
ASUS beep sounds and causes
● If the beep sounds once briefly
It is starting normally.
● If you hear one long beep and two short beeps.
No memory detected. The problem may be resolved by removing and reinserting the memory or cleaning the memory slot and surrounding area.
● If the beep sounds once long and then three times briefly.
The graphics memory may not be detected or may be defective.
Please try connecting again.
● If the beep sounds four times for a long time
The CPU may not be compatible with the motherboard, or the BIOS may be an older version. Please check CPU compatibility and try updating the BIOS.
Mac beep sounds and causes
● If a beep sounds once every 5 seconds
Memory may not be detected.
Try re-inserting and re-inserting the memory and making sure it is firmly installed.
● 3 beeps every 5 seconds
If the memory fails the consistency check.
In this case, please make sure that the memory is firmly installed.
● If the beep sounds 3 long times, 3 short times, and then again 3 times longer.
This is when your Mac is restoring firmware.
bar appears and then it seems to start normally.
Fujitsu beep sounds and causes
● If it sounds 1-2
There may be a problem with the BIOS or motherboard.
Try draining the motherboard button battery and cleaning the motherboard.
● If it sounds 1-1-1-1
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If it sounds 1-3-3-1
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If it sounds 1-3-3-2
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If it sounds 1-3-4-1
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If it sounds 1-3-4-3
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If it sounds 1-4-1-1
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If it sounds 4-3-4-3
There may be a memory test error.
Please check the memory connection and try cleaning the slot.
● If the sound 1-1- continues to sound for a long time.
This is when the power cable is not connected to the graphics card.
First, turn off the power and connect the power cable to the graphics card.
Please wait at least 10 seconds before turning on the power again.
Causes and solutions when the PC does not start even though the fan spins for a moment
If you try to start your computer and the fan only spins for a moment but does not start, you should suspect a problem with the power supply unit or motherboard.
Please check the power supply unit with a tester and replace it if it appears to be defective.
Causes and solutions when the laptop won't start but the fan spins or keeps spinning
If your laptop won't start but the fan spins or keeps spinning, try the solutions below.
→Causes and solutions when the PC does not start but the fan spins
Summary of causes and solutions when the PC does not start but the fan is spinning
This time, we explained the causes and solutions when the computer does not start but the fan spins.
If the fan is spinning, there is usually no problem with the power supply, so it is most likely caused by a malfunction in another part.
First, if it's a desktop computer, check to see if it's properly connected to the monitor, and if the monitor is malfunctioning or turned off.
If you have a laptop, the backlight may be out.
You may also notice the fan spinning or making beeping noises.
In such cases, you may be able to determine the cause and solution based on the beep sound, so it is a good idea to refer to the manufacturer's website.