Why is my power supply not working?

A power supply may not be working due to a range of issues, from simple loose connections and external factors to more complex internal component failures or physical damage. Diagnosing the exact cause often involves systematic troubleshooting.

Why Is My Power Supply Not Working?

A non-functional power supply (PSU) can halt your entire system. pinpointing the exact issue requires careful inspection and testing, as problems can range from external power faults to internal hardware failures.

Common Reasons Your Power Supply Might Fail

Understanding the typical causes of PSU failure can help in diagnosing the problem.

1. Connection Issues

Loose or improperly seated cables are among the most frequent culprits.

• AC Power Cable: Ensure the power cable connecting your PSU to the wall outlet (or surge protector) is firmly plugged in at both ends. Test with a different power outlet or a known-working cable.
• Internal Power Cables: All internal connectors must be securely seated. This includes:
  • 24-pin ATX Connector: The main power cable to your motherboard.
  • 4/8-pin CPU Power Connector: Supplies power specifically to the CPU.
  • PCIe Power Cables: For dedicated graphics cards (often 6-pin, 8-pin, or 6+2-pin).
  • SATA/Molex Power Cables: For storage drives and other peripherals.
  • Inspect for Damage: Thoroughly examine the connectors. Look for any obvious signs of physical damage, such as bent or broken pins on the connectors. Ensure that all connectors are securely seated in the power supply as well as the device it is connected to.

2. Physical Damage and Overheating

Visible damage can be a direct indicator of a PSU problem.

• External Damage: Accidental impacts or liquid spills can render a PSU inoperable.
• Internal Component Damage: Look for visible signs of internal damage, such as cracked or discolored components on the circuit board if you can safely inspect it (only do so if you are comfortable and the unit is unplugged).
• Signs of Overheating: Overheating can severely damage internal components. Signs include a strong burning smell, melted plastic, or scorched areas. These are critical indicators of a serious fault. Overheating can occur due to insufficient cooling, dust buildup, or an overloaded PSU.

3. Internal Component Failure

Over time, components within the PSU can degrade or fail.

• Capacitor Failure: Capacitors regulate voltage and smooth power delivery. Swollen, leaking, or burst capacitors are common failure points.
• Voltage Regulator Issues: Problems with voltage regulators can lead to incorrect voltage output, causing instability or outright failure.
• Short Circuits: An internal short circuit can trip the PSU's protection mechanisms, preventing it from powering on, or cause irreparable damage.

4. Overload or Inadequate Wattage

If your system demands more power than your PSU can supply, it might fail to start or experience instability.

• Underpowered PSU: Adding new, power-hungry components (e.g., a high-end graphics card) without upgrading the PSU can lead to it being underpowered for the system's needs.
• Aging PSU: As PSUs age, their efficiency can decrease, making them less capable of delivering their rated wattage, especially under load.

5. External Electrical Issues

Problems outside the PSU itself can prevent it from functioning.

• Faulty Wall Outlet/Surge Protector: Test the PSU with a different wall outlet or bypass the surge protector to rule out external power supply issues.
• Power Surges/Brownouts: Sudden fluctuations in mains power can damage a PSU, especially if it lacks robust protection features.

6. Safety Mechanism Activation

Modern PSUs include various protections that can trigger, preventing damage but also stopping the unit from working.

• Over-Voltage Protection (OVP): Shuts down if output voltage exceeds a safe limit.
• Under-Voltage Protection (UVP): Shuts down if output voltage drops below a safe limit.
• Over-Current Protection (OCP): Shuts down if current drawn on a rail exceeds its limit.
• Short-Circuit Protection (SCP): Shuts down if a short circuit is detected.

Troubleshooting Steps

Before concluding your PSU is dead, perform these checks:

1. Visual Inspection: As mentioned, look for physical damage: bent pins, cracked components, discoloration, or signs of overheating. Ensure all wires are firmly connected.
2. Test the Outlet: Plug a different device into the power outlet to confirm it's working.
3. Cable Check: Replace the AC power cable with a known-good one.
4. Paperclip Test (Bridging Pins): For ATX power supplies, you can perform a paperclip test to see if the PSU fan spins. This involves shorting the green wire (Power-On) to any black wire (Ground) on the 24-pin connector while the PSU is unplugged from the wall and disconnected from all components. If the fan spins, the PSU might be partially functional, indicating the issue could lie with other components (e.g., motherboard). If it doesn't spin, the PSU is likely faulty.
   • Caution: This test should only be performed by individuals comfortable with basic electronics. Always ensure the PSU is disconnected from the wall before making any internal connections, and never perform this test with the PSU connected to your computer. For a detailed guide, refer to sources like How to Perform a PSU Paperclip Test (though using a multimeter is safer and more informative).
5. Multimeter or PSU Tester: For a more precise diagnosis, a power supply tester or a multimeter can measure the voltage output on different rails. This requires technical knowledge and careful handling.
6. Component Isolation: If possible, disconnect all non-essential components from the PSU (graphics card, drives) and try to boot with just the motherboard, CPU, and RAM. If it starts, add components back one by one to identify the faulty part.

When to Replace Your Power Supply

If you've performed the troubleshooting steps and suspect the PSU is the cause, replacement is often the most straightforward solution. Choose a reputable brand with sufficient wattage for your current and future system needs, ensuring it has necessary safety features.

Summary of Common Symptoms and Checks

Symptom	Possible Cause	Quick Check
System won't turn on (no lights, no fans)	Dead PSU, loose power cable, faulty outlet	Check AC cable, test different outlet, perform paperclip test on PSU. Look for physical damage.
System powers on then immediately off	Overload, short circuit, PSU protection engaged	Disconnect non-essential components, check for internal shorts (e.g., faulty component).
Random reboots or crashes	Unstable voltage, failing PSU	Check PSU fan for spinning, listen for unusual noises. Use monitoring software for voltage readings if possible.
Burning smell or visible smoke	Overheating, component failure, short circuit	Immediately unplug PSU. Visually inspect for burned components. Do not attempt to restart.
Bent/broken pins on connectors	Physical damage, improper installation	Carefully inspect all power connectors for damage. Ensure they are securely seated.