Member Avatar for sternssixthree

Hi,

Just asking if anyone knows how to test a psu fan once its been disconnected from the psu itself? i know i can test the whole thing by rigging the motherboard pins, but just the fan? im trying to use the fan from an old psu as additional coolng, but cant splice it to my existing psu because theres already another one spliced to it!


Thanks

  • 2 Contributors
  • 2 Replies
  • 133 Views
  • 1 Day Discussion Span
  • Latest Post Latest Post by OlyComputers

Dani AI

Generated

A short, practical checklist to safely test and re-use that PSU fan, with a few corrections to earlier posts.

First, identify the fan before applying power. Look for a label or part number on the hub and confirm the rated voltage and connector type (many case/PSU fans are 12 V and use 3- or 4-pin headers; some older or unusual fans differ). If the label is gone, search the part number online or inspect the wiring and connector shape — the fan spec is the key. See general connector and voltage info at Computer fan.

Safe bench-testing method:

  • Use a variable DC supply or a 12 V DC adapter sized above the fan’s current draw. If using a lab supply, set a low current limit (for typical 80–140 mm fans, 0.3–0.5 A is plenty) and raise voltage slowly to the rated value while watching for abnormal noise or high current.
  • If you must use a PSU to power the fan alone, start the PSU safely (short PS_ON to ground) and connect the fan via a proper adapter — avoid hot-splicing wires inside the case. Refer to ATX guidance before trying the PS_ON trick: ATX.

Wiring and mounting tips:

  • Don’t assume wire colors are identical between fan plugs and peripheral Molex harnesses; verify which wire is + and which is ground before connecting. Use a Molex-to-fan adapter or a purpose-made splitter when possible. For a tidy, reliable permanent install, use crimp connectors or solder and heat-shrink — avoid exposed joins.

Troubleshooting:

  • If the fan hums, won’t start, or vibrates, check bearings by trying to spin the hub gently by hand (power off). A seized or noisy bearing usually means replacement is the safer, quieter option. If uncertain about the fan’s specs, post the label text or a clear photo so others can help identify it.

Recommended Answers

All 2 Replies

Member Avatar for sternssixthree

as in could i just hook it up to a 12v dc battery?

Member Avatar for OlyComputers

I'm a little confused on this, are you tryign to splice the fan from an old PSU into power for additional cooling on your case, or coolinf for your PSU?

It wont run on 12v, I'm pretty sure that those fans are 5v. Try splicing it to a molex socket and just plugging it into the power supply, if you dont' have a spare molex to use you could splice it into the power strands coming out of the PSU or the same ones that are hooked up to the existing fans.

REMEMBER: desktop PSUs run lines at two different voltages, there are red 5v strands and yellow 12v strands. be sure to color match to the wire on the fan or else you're liable to toast your fan (have to rewire it at teh very least).

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.