Troubleshooting Computer Hardware Issues: No Signal on Monitor Despite Fan Running

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Many friends are confused about whether the failure is a software fault or a hardware fault. Software faults include issues caused by the operating system and applications, while hardware faults are caused by damage to computer hardware. In simple terms, if the monitor displays content when powered on, it is likely a software fault; if the monitor shows no signal and does not display anything, it is a hardware fault. Below, we will discuss how to handle the hardware fault of the host fan running but the monitor showing no signal and no display.

1. Check the Appearance

Check if the power indicator light on the monitor is on, if the monitor power is turned on, if the monitor power cable is plugged in properly, and if the power strip is functioning. If there is a dedicated graphics card, check if the monitor signal cable is connected to the dedicated graphics card.

2. Check the NUM Lock Light on the Keyboard

After powering on, press the NUM key on the numeric keypad. If the NUM light turns on and then off with another press, the host has successfully started, and you only need to check the monitor, monitor signal cable, and graphics card for faults.

If there is no response from the NUM key, you will need to open the case and check further.

If there is no NUM key on the keyboard, you can press the Caps Lock key and observe the Caps Lock light.

3. Disassemble the Machine

Disassembling the machine can resolve issues caused by static electricity, poor contact, etc. Note: Always turn off the power!

1. Turn off the power and remove the side panel of the case;

2. Remove the dedicated graphics card, memory, and motherboard battery, and set them aside for later use;

3. Use a hairdryer to clean the dust inside the case;

4. Check the motherboard for any bulging capacitors or burn marks;

5. Use an eraser to clean the golden fingers on both sides of the memory and graphics card;

6. Reinstall the motherboard battery, install one memory stick in the slot farthest from the CPU;

7. Power on the machine and test it. Press the NUM key on the keyboard to check if it starts normally. If the NUM light functions correctly, sequentially install the remaining uninstalled graphics card and memory to test and identify the faulty component;

8. If after following the above steps the NUM light does not respond, does not light up, or does not turn off, and if you have multiple memory sticks, swap them out and test again, checking each memory slot one by one;

9. After testing all memory and slots, if it still does not start, remove the CPU cooler and power on the machine. Touch the top of the CPU to check if it is warm; if the CPU is not heating up, the motherboard is likely faulty;

10. If you have spare parts or another machine, you can swap components to test their functionality and identify the faulty hardware to replace it.

4. Tips

1. If the keyboard NUM light, Caps Lock light, or if there is no keyboard, press the main power button. If you can turn off the machine normally, it is functioning properly; if you have to hold the power button to turn it off, there is a hardware fault.

2. Hardware fault rates: power supply > motherboard > graphics card > memory > CPU, for reference only.

3. Motherboard diagnostic lights: CPU, DRAM (memory), VGA (graphics card), BOOT (system or hard drive). Under normal startup conditions, they will light up sequentially, and the one that stays lit indicates the issue. If the CPU light is on, it indicates that the CPU is undetectable or faulty. If the DRAM light is on, it indicates that the memory is undetectable or faulty. If the VGA light is on, it indicates that the graphics card is undetectable or faulty. If the BOOT light is on, it indicates that the boot device (e.g., hard drive) is undetectable or faulty.

4. Common alarm sounds from a computer with a buzzer:

One short beep: normal startup;

Two short beeps: conventional errors, correct BIOS settings;

One long and one short beep: memory or motherboard error, can be resolved by replacing memory or motherboard;

One long and two short beeps: monitor or graphics card error, replace and test;

One long and three short beeps: keyboard controller error, check the motherboard;

Continuous long beep: memory not seated properly or damaged, check the tightness of the memory;

Continuous short beeps: power supply issue.

If the above methods do not resolve the issue, or if you cannot find the faulty component, please take the computer to a repair shop!

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