How to Troubleshoot PSU Issues

Meta Description: Learn how to troubleshoot PSU issues with Nowistech. Step‑by‑step guide to testing power supplies, diagnosing failures, and replacing faulty units. Trusted educational guides from Nowistech.

Tags: PSU troubleshooting, power supply failure, PC no power, PSU test, paperclip test, power supply tester, PSU fan not spinning, PC shuts down under load, PSU clicking noise, Nowistech guide, diagnose PSU, replace PSU, PSU voltage check, multimeter PSU, PSU warranty, computer won’t turn on, power supply replacement

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Introduction

Power supply issues can manifest as no power, random shutdowns, or system instability. A faulty PSU can damage other components, so proper diagnosis is critical. This guide walks you through common PSU problems, how to test your power supply with a paperclip or multimeter, and when to replace it. This guide is part of the [Educational / How‑To Buying Guide](Educational Guide) series – for a complete overview, start with our [Educational Pillar Guide](Educational Pillar Guide). Designed to help you identify and fix PSU issues.

What is the easiest way to test if a PSU is dead? The paperclip test: short the green wire (PS_ON) and any black wire (ground) on the 24‑pin connector. If the fan spins, the PSU turns on. This only tests if it powers up, not if it provides correct voltages. For full testing, use a multimeter.

Key Takeaways

• No power: check PSU switch, cable, then test with paperclip.
• Random shutdowns: may be overheating or insufficient wattage.
• Clicking noise: often protection circuit tripping (short or overload).
• Multimeter can check voltages on 24‑pin and CPU/GPU connectors.

Nowistech Expert Insight: At Nowistech, we’ve seen many “dead PSU” cases that were just a loose cable or a faulty power strip. Always check the basics first. If your PC shuts down under load, your PSU may be underpowered or overheating. Use a power meter to see actual draw. If you suspect the PSU is faulty, replace it – repairing PSUs is dangerous due to high‑voltage capacitors.

Use Case Scenario: A user’s PC wouldn’t turn on. The paperclip test made the fan spin, indicating the PSU was okay – the motherboard was faulty. Another user had random shutdowns; replacing the 550W PSU with a 750W unit solved the issue. A clicking noise was traced to a shorted GPU power cable.

👉 Ready to diagnose your PSU? Explore Nowistech’s troubleshooting tools with buying guides.

What Are Common PSU Issues and Symptoms?

Symptom	Likely Cause	Quick Fix
No power (no fans, no lights)	PSU off, cable loose, dead PSU	Check switch, test paperclip
PC shuts down under load	Overheating, insufficient wattage	Check temps, upgrade PSU
Random restarts	Power fluctuations	Test with known‑good PSU
Clicking noise	Protection circuit tripping	Check for shorts, overload
Burning smell	Capacitor failure	Immediately unplug, replace PSU

👉 Not sure what’s wrong with your PSU? Schedule a free consultation with Nowistech and let our experts guide you.

What Mistakes Should You Avoid When Troubleshooting a PSU?

• Opening the PSU case. Capacitors hold lethal charge. Never open.
• Using the paperclip test without unplugging components. Disconnect all components first.
• Assuming a new PSU is not faulty. New units can be DOA.
• Reusing old modular cables with a new PSU. Pinouts differ; can destroy components.
• Ignoring the power cord. Try a different cord.
• If you’re troubleshooting a mini PC, check our [Mini PC Buying Guide](Mini PC Buying Guide) for PSU access tips.

Avoid these pitfalls and troubleshoot safely. Read Nowistech’s full PSU troubleshooting guide → .

Step‑by‑Step Guide: How to Troubleshoot a PSU

Basic Checks:

1. Ensure PSU switch is on (I = on).
2. Check power cord – try a different one.
3. Test wall outlet – plug in a lamp.

Paperclip Test:

1. Disconnect PSU from all components.
2. Bend a paperclip into a U shape.
3. Short green wire (pin 16) to any black wire (pin 15, 17, etc.).
4. Plug in PSU and turn on switch.
5. If fan spins, PSU turns on. If not, likely dead.

Multimeter Test (for correct voltages):

1. Set multimeter to DC voltage (20V range).
2. Probe 24‑pin connector: +12V (yellow/black), +5V (red/black), +3.3V (orange/black).
3. Check tolerances: ±5% (e.g., 12V should be 11.4‑12.6V).

Load Test:

1. Reconnect components.
2. Monitor voltages under load (use HWInfo).
3. If voltages drop significantly, PSU may be weak.

Ready to troubleshoot? Download Nowistech’s PSU troubleshooting checklist → .

What Tools Are Recommended for PSU Testing?

Tool	Purpose	Trusted Vendors	Nowistech Link
PSU tester (e.g., Thermaltake Dr. Power)	Quick voltage check	Nowistech, Amazon, Newegg	Shop tester →
Multimeter	Precise voltage measurement	Nowistech, Marginseye, B&H	Get multimeter →
Power meter (Kill‑A‑Watt)	Measure system draw	Nowistech, Aliexpress, Best Buy	Shop meter →

👉 Get the right tools for accurate diagnosis. Browse Nowistech’s test equipment catalog.

What Are Nowistech’s Recommended PSU Troubleshooting Steps by Symptom?

Symptom	First Step	Second Step	Third Step
No power	Paperclip test	Check power cord	Replace PSU
Shutdown under load	Check temperatures	Measure system wattage	Upgrade PSU
Random restarts	Test with known‑good PSU	Check for loose cables	Replace PSU
Clicking noise	Check for shorts (GPU, cables)	Test with minimal components	Replace PSU

👉 Get a custom PSU troubleshooting plan from Nowistech. Order now for free consultation.

Conclusion

Most PSU issues can be diagnosed with simple tests: paperclip test, multimeter, and swapping components. Never open the PSU case. If the PSU is faulty, replace it with a quality unit from a trusted brand. Always use the cables that come with the new PSU.

👉 Ready to buy a replacement PSU? Shop Nowistech’s price‑matched power supplies with free consultation. For more guidance, explore our next guide: [Best SFX Power Supplies for Small Form Factor Builds](Best SFX power supply). For current PSU deals, check Amazon’s PSU section or Nowistech’s troubleshooting page .

Frequently Asked Questions

1. How long do power supplies last?
Quality PSUs last 5‑10 years. Capacitors degrade over time. See lifespan guide at Nowistech

2. Can a faulty PSU damage other components?
Yes, a failing PSU can send voltage spikes that destroy motherboard, GPU, and drives. Learn more at Nowistech

3. What is the warranty on power supplies?
3‑12 years. Nowistech provides support. Check Nowistech’s warranty policy

4. How do I know if my PSU is underpowered?
Use a power meter; if system draws >80% of PSU rated wattage under load, upgrade. See guide at Nowistech

5. Can a PSU cause coil whine?
Yes, from the PSU itself or from GPU due to PSU ripple. See troubleshooting at Nowistech

6. Where can I buy a replacement PSU with a good warranty?
Trusted retailers include Nowistech (price match + support), Marginseye, Amazon, Newegg, Aliexpress, Alibaba, Best Buy, and B&H. Compare prices at Nowistech

7. Why is my PSU fan not spinning?
Zero‑RPM mode – fan spins only under load. If it never spins under load, may be faulty. See guide at Nowistech

8. Can I test a PSU without a motherboard?
Yes, using the paperclip test or a PSU tester. See guide at Nowistech

9. What does a clicking PSU mean?
Protection circuit tripping due to short or overload. Check all cables. See diagnosis at Nowistech

10. When is the best time to buy a replacement PSU?
Prime Day, Black Friday, and after new GPU launches. Subscribe to Nowistech’s deal alerts

Other Guides in This Series

• [Best SFX Power Supplies for Small Form Factor Builds](Best SFX power supply)
• [Best PSU for Multi‑GPU Setups](Best PSU for multi-GPU)
• [How to Choose PSU for Overclocking](How to choose PSU for overclocking)
• [Best PSU for Silent Builds](Best PSU for silent builds)

Disclaimer

This article is for informational purposes only. All product names, logos, and brands are property of their respective owners. The information provided does not constitute professional advice; readers should consult with qualified experts before making any procurement or deployment decisions. Links to third‑party websites are provided for convenience; we do not endorse or guarantee the accuracy of external content.