PSU failure symptoms - how to spot a failing power supply

The power supply is the component everyone forgets and the one fault that can damage everything else on the way out. A failing PSU rarely announces itself - instead it produces symptoms that look like every other component failing at once.

The symptoms

Random shutdowns under load. The classic sign. The system powers off instantly - no blue screen, no warning, just off - when you start a game or render. Load is when the system draws the most power, and a degraded PSU can't deliver it.

Random restarts. Similar to shutdowns, but the system reboots itself. Voltage dipping momentarily below what the motherboard needs triggers an immediate reset.

Failure to turn on - sometimes. Intermittent cold-start problems, where the PC needs several presses of the power button, or only starts after being left unplugged, point strongly at PSU capacitor degradation.

Crashes that look like GPU or RAM faults. Unstable power produces application crashes, driver timeouts, and memory errors that pass every component test. If you've tested everything else and found nothing, the PSU is the prime remaining suspect.

Audible warnings. Coil whine from the PSU under load isn't necessarily a fault, but new or worsening noises are. Clicking, buzzing, or a fan that's grinding or has stopped spinning entirely all mean the unit needs attention.

Burning smell. A faint electrical or burnt-plastic smell from the PSU area is a stop-everything sign. Power off, unplug, and don't use the machine until it's been looked at.

Why PSUs degrade

PSUs are built around capacitors, and capacitors age. Heat accelerates the process dramatically - a PSU in a poorly ventilated case, clogged with dust, ages several times faster than one that runs cool.

The practical effect is that a PSU's real-world capacity falls over time. A quality 650W unit may deliver its rating for years; a budget unit may struggle to deliver 500W cleanly after three. This is why a system that was stable for years can become unstable after a GPU upgrade - the PSU was already degraded, and the new card pushed it past what it can still deliver.

Power cuts and surges also take a toll. A PSU that's absorbed a serious surge may keep working but with damaged protection circuitry, leaving everything downstream exposed to the next one.

How to test it

Honestly: properly testing a PSU at home is difficult, and this is one of the few components where that's the case.

The paperclip test (bridging green to black on the 24-pin connector with the PSU disconnected from everything) only tells you the PSU turns on. A failing unit passes this test happily.

Multimeter checks on the rails at idle will usually read fine too, because most PSU faults only appear under load. Without an electronic load tester, you can't see voltage sag, ripple, or instability at the wattages where the problems live.

Software voltage readings in HWiNFO are taken from the motherboard's sensors and are notoriously imprecise - useful for spotting wild swings, not for judging a PSU healthy.

The most practical home test is substitution: borrow or use a known-good PSU of adequate wattage. If the symptoms vanish, you have your answer.

Don't gamble on a failing PSU

A worn PSU isn't just a stability problem - it's a risk to the rest of the machine. The PSU's job includes protecting downstream components from overvoltage and surges. As units degrade, that protection degrades with them, and a catastrophic PSU failure can take the motherboard, drives, and GPU with it.

This is also why ultra-cheap no-name PSUs are a false economy in the first place: the protections are often minimal or absent even when new. If you're replacing a unit, buy a reputable brand with an 80 Plus rating and enough headroom for your hardware plus 20-30%.

When to stop and send it in

If your system is randomly shutting down, restarting, or failing to start - and you've ruled out overheating and the obvious suspects - get the PSU tested properly before it fails terminally. We test PSUs under controlled electronic load on the bench, measuring voltage stability and ripple at realistic wattages, which is the only way to confirm a unit is genuinely healthy. If it's failing, you'll know before it takes anything else with it.