Common computer faults: what they mean and what to do

Computers fail in fairly predictable ways. Whether you have a desktop tower, an ageing laptop, or a compact mini-PC, the underlying causes of most faults are the same: heat, failing storage, bad power, or degraded components. Knowing which category your problem falls into saves time, money, and the risk of making things worse.

This guide covers the most common faults in plain terms, what you can safely check yourself, and when the job genuinely needs professional tools.

The machine will not start at all

A completely dead machine is one of the more alarming symptoms, but it is often one of the easier faults to narrow down.

What to check first:

1. Test the power supply independently. For a laptop, try a known-good charger of the correct wattage. For a desktop, listen for the power supply fan spinning — if nothing moves when you press the power button, the PSU or its fuse is the first suspect. 2. Inspect the power port on a laptop for bent or corroded pins. A damaged DC jack is one of the most common mail-in repairs we see. 3. Remove any external drives, USB hubs, or docking stations. A faulty peripheral can prevent POST. 4. On desktops, reseat the RAM sticks — press them firmly until both clips click. Loose RAM causes total boot failure and costs nothing to check.

When it is probably not DIY: If the power rail tests fine but the machine still does not respond, the fault is likely on the motherboard — a blown fuse, a failed voltage regulator, or a damaged charge circuit. These require a multimeter and soldering tools to diagnose safely.

Overheating and excessive fan noise

Laptops are particularly prone to thermal problems because the airflow path is narrow and fills with dust and lint over two or three years of use.

Symptoms: the machine shuts down suddenly under load, the chassis is hot to touch near the vents, or the fans run at full speed constantly.

What you can do:

1. Use compressed air to blow out the vents from the exhaust side. Do not spray liquid into the machine. 2. Check whether the machine is sitting on a surface that blocks the intake vents (soft furnishings are a common culprit). 3. Run a free utility such as HWMonitor (Windows) or iStat Menus (macOS) to read the CPU temperature. Anything above 90 °C under light load points to a thermal compound or airflow problem.

When it needs a workshop: If blowing out the vents does not help, the heatsink needs to be removed and the thermal compound replaced. On most laptops this means taking the entire bottom panel off, disconnecting the fan, and working around the motherboard. Done incorrectly you risk stripping screw threads, snapping ribbon cable connectors, or cracking the heatsink mount. This is a common mail-in job that typically takes under an hour with the right tools.

Slow performance

Slow computers are frequently misdiagnosed. Before assuming the hardware is failing, rule out the software causes.

1. Check Task Manager (Windows) or Activity Monitor (macOS) to see whether a single process is consuming most CPU or RAM. 2. Run a full malware scan with Malwarebytes Free. 3. Check how full the storage drive is. Windows and macOS both degrade noticeably when a drive is above 85–90% full. 4. If the machine has a hard disk drive (HDD) rather than a solid-state drive (SSD), replacing the HDD with an SSD is often the single most effective upgrade you can make to an older machine. On most laptops and desktops this is a straightforward job if you are comfortable with basic disassembly.

Warning sign: If performance has dropped suddenly rather than gradually, and the drive is making clicking or grinding noises, stop using the machine immediately. A clicking hard drive is a sign of mechanical failure. Every power cycle risks further damage and reduces the chances of data recovery.

Screen problems

Screen faults on laptops range from easy to complex depending on the symptom.

• Backlight works but image is faint or washed out — the LCD panel itself is usually fine; the display cable or inverter board may be failing.
• Half the screen is dark, or there are horizontal lines — the panel is damaged, or the display cable has been pinched in the hinge (common on machines that are opened and closed thousands of times).
• No image at all, but an external monitor works — the GPU output path is intact; the fault is in the panel, cable, or display connector on the board.
• No image on any output — GPU or firmware fault. Needs professional diagnosis.

Screen replacements are achievable on many laptops with a plastic spudger, patience, and a replacement panel ordered to the exact model number. The risk is tearing the display cable during removal, which is fragile on thin-bezel machines. If you are not confident, send it in.

Storage failure and data

SSD and HDD failure are the two faults where acting quickly matters most.

1. Run CrystalDiskInfo (Windows) or Disk Utility (macOS) to check the drive health status. Any reported reallocated sectors, pending sectors, or uncorrectable errors are serious. 2. Back up immediately if you have not already done so. Do not wait until the drive has fully failed. 3. A drive that is not detected at all, or is detected intermittently, should be treated as failing even if the health report looks clean.

Data recovery note: If a drive has already failed mechanically, software recovery tools will not help and may make things worse. Professional recovery from a mechanically failed drive is expensive — prevention by backing up regularly is always the better option.

What you should not attempt without experience

• BGA reballing or GPU reflow. This requires a hot air station, precise temperature profiles, and practice on donor boards. The "oven trick" and heat gun methods seen online cause uneven heating that worsens the fault.
• Liquid damage repair. Corrosion spreads quickly. The machine needs to be powered off, disassembled, and cleaned with isopropyl alcohol within hours of an incident. Attempting to power on a liquid-damaged machine before it is properly cleaned often causes secondary faults that would not otherwise have occurred.
• BIOS/firmware recovery on locked machines. Some machines require a programmer and a chip clip. Attempting this without the correct tools risks permanently bricking the board.

When to mail it in

If the fault is beyond a simple clean, reseating, or drive replacement — or if you have opened the machine and the problem has not improved — a mail-in repair is worth considering. At Hark Tech we carry out component-level repairs on laptops, desktops, and other electronics, including board-level diagnosis, thermal work, screen replacements, and data recovery from failing drives. Most repairs are turned around within a few working days. Send a description of the fault via our contact page and we will give you an honest assessment before you commit to sending anything.