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What happens when a PSU fan stops?

By Reachable ยท 8 replies
Apr 18, 2010
  1. Does anybody have any experience or knowledge of what happens when a PSU fan suddenly dies while the unit is on? Do PSUs generally automatically turn off when that happens, or do they continue to run and heat up until they fry themselves and the rest of the components along with them?

    I have a six year old PSU that has run (estimated liberally) about half of all elapsed hours during that time. Lately it's been sounding somewhat louder than it had been. I would rather replace it now than court disaster.

    Thanks in advance to respondents, and I ask your forgiveness if this question has been asked before.
  2. Route44

    Route44 TechSpot Ambassador Posts: 11,979   +71

    Replace a.s.a.p. unless you want to try and fix it yourself which will cost you in funds no matter how you look at it. Purchase a good one.
  3. Ritwik7

    Ritwik7 TechSpot Chancellor Posts: 1,672   +9

    I'll second Route on that. Replace the PSU before it overheats and causes any electrical damage to your system.
  4. Joneswilliamsc

    Joneswilliamsc TS Rookie

    If a fan breaks than it is a really very bad news. I would suggest that you open your PC up and check the fans manually. You have to be sure to turn off the power first and disconnect the main power cable.
  5. Reachable

    Reachable TS Booster Topic Starter Posts: 106   +29

    I replaced the PSU with a very good one that serves my requirements excellently.

    Replacing a fan in a power supply unit is a dangerous undertaking. There are capacitors inside the PSU that could possibly deliver a fatal electric shock, and they retain their charge even when the unit is off and not plugged in, and they can retain their charge for months at a time. There are ways to discharge the capacitors, but none of the techniques can be considered certain enough to remove risk. Do not open a PSU unless you know what you're doing.

    Thanks for the replies.
  6. Route44

    Route44 TechSpot Ambassador Posts: 11,979   +71

    Good to hear! We take it the system is running stable, correct? By the way, what psu did you settle on and how much power?
  7. Reachable

    Reachable TS Booster Topic Starter Posts: 106   +29

    I got a Nexus Value 430 (430W). I was actually replacing another Nexus, a 300W unit which was about the quietest (a top priority) in its day. The newer model is actually significantly quieter by design. It also tests high in efficiency at all power levels. My system is running stable.

    I had wondered whether good PSUs have a thermal sensor that would shut the unit down at a certain temperature. In either case, a replacement was called for, and the urging on this thread helped promote it.
  8. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    I think many of the lower watt PSUs, say below 350W or so, could probably run 'ok' without a fan. They probably just were just less capable of delivering the upper end of their power as they got hotter. But with higher capacity PSUs in roughly the same size area a fan dying would be more catastrophic.

    Also, while I wouldn't recommend replacing a fan to everyone, I'm not incredibly experienced with circuits and such, and I've replaced the fan on one of mine before. I think most PSUs don't have them hard wired into the board, they use a connector instead. So its really as simple as disconnecting it and connecting a new one. It shouldn't be THAT hard to avoid touching the caps.
  9. Reachable

    Reachable TS Booster Topic Starter Posts: 106   +29

    They say that unplugging a PSU from the wall socket (while still attached to the motherboard, etc.) and then pressing the power button on the case once or twice, will discharge the caps. Again, one should not bet one's life on it.

    I had a 145W power supply that came with a small case, and I used it with an extremely low-powered system (an AMD Geode) . I swapped out the fan. Without getting into the details, something went awry (not what would usually happen; as SNGX1275 said, it's usually straightforward) and the fan appeared to spin for a while and then apparently stopped. Fortunately I discovered it before too long, but the PSU had gotten horrendously hot and the system was almost fried.

    This makes me think that you should not risk running a PSU, no matter how low power, without a fan, unless it's a specially designed fanless PSU.
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