PSU Troubleshooting: Most Common Issues

Quick Answer

PSU failures most often trace back to inadequate wattage for your components, poor ventilation causing thermal shutdowns, and degraded capacitors in budget units. Knowing what to look for saves you from unnecessary component swaps and costly diagnostic visits.

Why Your PC Won't Power On At All

A completely dead system is alarming, but it's often the easiest PSU symptom to isolate. Check the wall socket, the power cable, and the rear PSU switch first. If the system still won't respond, unplug everything except one stick of RAM, the CPU, and the motherboard, then try again. No response points squarely at the PSU.

A paper clip test confirms whether the PSU itself is functional. Disconnect it from the motherboard, short the green wire (PS_ON) to any black wire on the 24-pin connector, then flip the PSU on. If the fan doesn't spin, the unit is almost certainly dead. In SA, replacing a dead PSU means waiting 2 to 5 business days for delivery from most suppliers, so plan around that lead time.

Random Shutdowns and Restarts

If your PC cuts out mid-game or under load, the PSU is struggling to deliver sustained power. Three likely causes: the unit is undersized for your components, the fan has seized and thermal protection is kicking in, or capacitors are failing.

Gaming rigs with an RTX 4070 or RX 7800 XT need at least a 650W unit with an 80 Plus Bronze rating. Running a GPU-heavy system on a 500W no-name PSU is a recipe for repeated shutdowns. Check the PSU fan through the ventilation grille and clean dust with compressed air before assuming the fan is dead.

Coil Whine and Strange Noises

Some electrical noise from a PSU is normal, but loud buzzing or high-pitched coil whine under load is worth investigating. If any noise is accompanied by a burning smell, shut the system down immediately , capacitor failure produces a burning odour before complete PSU death, and continuing to run risks damaging other components.

Frequently Asked Questions

How do I know if my PSU is undersized for my build?

Add up the TDP of your CPU and GPU, then add around 100 to 150W for storage, RAM, and fans. A quality PSU should sit at no more than 80% of its rated wattage under full load. If your draw approaches the rated output, you need a higher-wattage unit.

Can a faulty PSU damage other components?

Yes. A failing PSU can send voltage spikes through the 12V, 5V, and 3.3V rails, damaging the motherboard, RAM, and storage drives. Stop using the system rather than risk cascading failures far more expensive to fix.

Is it worth repairing a faulty PSU?

In most cases, no. Replacement is almost always the smarter financial call for budget units. For premium units like Corsair RMx series, manufacturer warranty claims are faster and safer than third-party repair.