How To Tell If Your Power Supply Is Bad?

One of the most frustrating things with PCs is when they simply don’t turn on. You don’t know exactly which part is bad or not working, and you are left wondering. 

A bad PSU won’t necessarily mean that your PC won’t start, and therefore it can be much harder to spot and diagnose. When not enough power is delivered to your PC’s parts, you might see crashes or lowered CPU and GPU performance.

Don’t worry, as we will show you how to spot some nuances where you can exactly tell that your PSU is not working correctly.

Why Do Power Supplies Go Bad?

dudty psu

During my internship at a PC and laptop repair shop, I spotted a familiar trend with many PCs that were sent to us as “Not booting.” The first thing I learned was to inspect the PSU. 

The most common issue was that a capacitor had blown up or melted, and thus power couldn’t be drawn from the wall to the PC’s hardware parts. 

Why do capacitors blow up, and are they the first component to malfunction? Well, it’s actually their job since they prevent physical damage to your other expensive hardware equipment. 

This can happen due to a power surge, unstable voltage, moisture buildup, or extreme temperatures

The other primary reason for a PSU failing are: 

  • It’s out of warranty or is nearing its life cycle
  • It has a defective hardware component causing irregular current
  • It’s overheating due to dust or poor airflow

PSUs are notorious for randomly going off. Sometimes, something goes wrong during their manufacturing process, or they go past quality control with a defect. 

Signs of a Defective PSU

There are definite signs of a dead power supply. Still, a dying or malfunctioning PSU could manifest as any common PC issues such as frequent crashes, blue screens, or freezing. All of which could result from any combination of software or hardware issues.

If you suspect that your PSU is dying, the only way to truly see if it’s at fault is to replace it with a different one and see if your other issues disappear. Anything from overheating to random shutdowns could be because of a failing PSU. However a dead PSU is much easier to point out, so read on to find out how?

Your Computer Won’t Correctly Start


The most obvious giveaway for a PSU not working is that your PC won’t start when you press the power button. You may notice that when you attempt to power your PC on, no fans start spinning, even though nothing is wrong with them. If your PC doesn’t have any flickering lights during startup, no picture on the screen, and the PSU fan doesn’t spin; it’s clear that your PSU is dead.

You have to note here that the symptoms might be similar when other PC parts start failing such as the GPU or the motherboard. The key difference when the PSU is at fault is when no other components show any sign of starting up.

Your Other PC Components Regularly Fail or Malfunction

The worst things about a faulty PSU are that it can cause hardware damage to your other components. That’s why a properly working PSU is vital in transferring the right amount of power to your parts. If you notice a pattern of hardware failure, such as your PC case fans constantly dying even when brand new, there is a high chance that a faulty power supply damages them.

  • Your PC will often still boot and appear to be working until you notice that you get regular hardware malfunctions with other parts.
  •  If a PSU is delivering too much or irregular power, this could overload your hardware parts. This is perhaps the main reason you should steer clear of refurbished PSU units.

You Noticed a Burning Plastic Smell or Smoke From Your PC Case

burned pc

If you ever noticed a burnt scent or any smoke from your PC, rest assured that some components got damaged. If you see either of these two, immediately power your PC down, open the case and inspect the motherboard and PSU for physical burn damage. Sometimes it might not be obvious, especially if it was a capacitor.

When overloading a capacitor, you will often hear a loud bang, indicating that it prevented an electric surge.

To check if your capacitors malfunctioned, check if they are severely discolored or darkened compared to the other healthy capacitors. While a skilled technician can easily change a single dead capacitor, if the issue is within the PSU, you will just have repeated incidents.

You Hear Buzzing or Clicking Sounds From Your Computer

This is perhaps the second biggest dead giveaway that your PSU is malfunctioning. Coil whine is a nerve-wrenching phenomenon in which you hear a high-pitched noise caused by electricity passing through a transistor. The thing is that it’s most often caused when your GPU is under load, but thankfully there is a straightforward way to tell if it’s your GPU or PSU. 

Check if it’s coming directly from the GPU or the back side of the case, where your PSU is located. Suppose you hear any loud noise or grinding sound from your PSU; it’s probably up for replacement. 

What to Do if Your PSU Is Not Working?

psu not working

When troubleshooting a PSU, there is only so much you can do. There are two main things that you can try:

  • Check if there is a loose cable connection. It might seem obvious, but if the PSU power cable is improperly connected, it might not deliver power to your other PC parts. Inspect all the PSU connector cables and double-check if they are 100% secured to the motherboard or your other components. 
  • Check if the ATX power cables are working. If you have an ATX power tester, you can use it to determine if the cables themselves are faulty and not delivering power. Alternatively, you can try swapping the ATX power cables for new ones. If you determine that a cable is defective, the replacement is incredibly cheap.

Except for the above-mentioned basic troubleshooting steps, unlike other PC parts, you don’t do any troubleshooting for a defective PSU, and you replace it with a new one. 

Suppose you risk tampering or opening your PSU for the sake of repair. In that case, a single wrong move can be a health hazard and possibly destroy your other PC’s electronic parts.

Never try to mess with or self-repair a PSU yourself. PSUs are relatively cheap compared to all other PC parts, so there is no excuse to use a damaged PSU in your system. The only thing you can safely do to your PSU for maintenance is to remove any dust with pressurized air.

How to Prevent PSU Damage in the Future?

psu damage

The most important thing to consider is always buying PSU units from reputable brands with customers’ solid product reviews and ratings. Even some major PSU manufacturers have a few bad batches, so please read up online and do extensive research before buying a PSU.

Never cheap out on your PSU! Always buy PSUs with a slight power overhead so that your system draw can never max your PSU’s capacity. You can calculate your system’s total power draw in idle or under load online. Never get the cheapest non-branded PSUs as they will last only a couple of months at best. In the end, you will be better off financially just investing in a more expensive but better-certified PSU. 

PSUs come with different efficiency certifications that go from bronze to platinum, depending on the actual percentage of power they can effectively use. As long as your PSU has a bronze certification, it underwent rigorous trials and tests to pass that standard.

The second thing you can do to prevent PSU damage is to keep it well ventilated. Ensure that you regularly clean your PC case from dust buildup, and always put your PC case higher up from the ground, as most PSU draws air from the bottom. 

If you have a carpet obstructing airflow, you are significantly shortening your PSU’s life. The less heat there is, the longer your parts will last and serve you for countless quality hours of work or gaming.

Related Questions

Am I Overloading My Power Supply?

The easiest way to know if you are overloading your PSU’s maximum Wattage capacity is to calculate all your PC’s parts’ power draw by adding their power draw together. 

For example, if your GPU is drawing 500 watts under load, and your CPU is drawing 300, that adds up to 800, so a PSU with anything less than that will be underpowered. 

Note that even if your PSU says that it supports 900 Watts and your system only draws 800, its actual effective power output could be lower depending on its energy certification. For example, a bronze class PSU will only offer 80% efficiency compared to a platinum one. 

Should You Repair Vs Buy a New PSU?

Never try to repair your PSU, besides just removing the dust from inside its case. There are PC repair shops that offer PSU diagnostics and repair. Still, from my experience working in a repair shop, even if we fixed the PSU, the customer would return a couple of months later with a dead PSU.

Is It Worth It to Buy a Refurbished PSU?

The power supply unit is the one part that you should never buy refurbished at any cost. Buying a used power supply is the worst since you never know what sort of abuse it went through with the past owner. There is no real way to tell unless you install it and your PC suddenly starts smoking. 

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