Member Avatar for AceX

Hey guys. It's not an old computer or anything. AMD Athlon X2 processor, NVidia Geforce 7900 GTX graphics card, 360GB SATA HDD, 2GB RAM, the works.

The problem is, that a couple days back one of the fans died on me. I kept it off for until I could get a new fan, which was no big deal. Plugged it in, powered it back up, etc. However, when it powered back up, it would receive power for a brief second (if that), then just completely turn back off. All the fans would start spinning, the lights turned on, and everything, but it turns off almost as soon as it turns on.

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  • Latest Post Latest Post by jaymz1972

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Symptom (brief): system powers on — LEDs and fans spin for a second — then everything cuts out. That pattern usually points to either the PSU going into protection (short/overcurrent) or the motherboard detecting a fault and forcing a shutdown. and have already signposted those possibilities; below are practical, low-risk steps to narrow it down and find the real fault.

Do a bench test outside the case. Put the board on cardboard or a wooden surface, fit CPU + cooler, one stick of RAM, and whatever video is required. Disconnect every nonessential cable (drives, front‑panel USB/audio, extra fans, PCI cards). Use the case power switch pins or a small screwdriver to momentarily short the power pins to start the board. If it stays on long enough to POST (or beep), the case or front‑panel wiring/standoff is a likely suspect.

Check the PSU rails and behavior. A PSU can spin up and then trip instantly if it senses a short or overloaded rail. A cheap PSU‑tester or a multimeter (if comfortable using one) will show whether +12V/+5V/+3.3V and the 5VSB are present and stable. If the failed fan was in the PSU, stop using that unit — PSU fan failure can cause internal damage.

Inspect the motherboard closely: bulging/burst capacitors, scorch marks, or stray screws/standoffs touching the PCB. If you get no POST beeps, attach a simple speaker to the motherboard headers to read beep codes. Try clearing CMOS (remove battery for a few minutes) to reset any BIOS fan‑monitor settings that could halt boot. If benching still fails and the PSU tests OK, the motherboard is likely damaged; if the board works but it fails in the case, recheck standoffs, front‑panel connectors, and any newly installed fan wiring.

Safety note: unplug mains before probing, discharge yourself to avoid ESD, and don’t attempt high‑voltage PSU internals—seek a shop if unsure.

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Member Avatar for OlyComputers

Could be a short in the motherboard or PSU, either from installing the new fan or whatever burned it out (probably not the latter if you were able to shut-down after it went out). Make sure you hooked up the new fan properly, and if possible try a different PSU (or get this one tested).

I'd also try taking out the new fan, just in case. As long as it wasn't the CPU fan turning the system on missing a fan wouldn't hurt anything. A computer can run in a normal climate can run fine without any case fans indefinately if the side panel is open (things will get a little warmer than you want, but it shouldn't over heat unless you're under very heavy load), or for a few minutes with the side panel closed. So don't worry about turning it on to test it.

Member Avatar for jaymz1972

Sounds to me that the system checkes if all the fans are present and connected. I had a similar problem with a notebook and found out one of the fans wasn't connected right. Does the system power up when you reinstall the damaged fan?

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