"Hot-plugging" fans to a power supply connector

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"Hot-plugging" fans to a power supply connector

Post by zoatebix » Wed Jan 07, 2009 11:04 am

It doesn't feel like a particularly good idea, but I can't think of a reason why plugging in (or unplugging) a fan would be any worse (or better) for the power supply than a hot-swappable drive.


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Post by protellect » Wed Jan 07, 2009 11:08 am

I've done it before, no harm done.

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Post by zoatebix » Wed Jan 07, 2009 12:58 pm

Good to hear!

Just for curiosity's sake, motherboard fan headers are a different animal and should be left alone while the computer is running, right?

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Post by nutball » Wed Jan 07, 2009 1:19 pm

No, you can hot-plug mobo fan headers too.

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Post by jammi » Thu Jan 22, 2009 6:18 pm

iv had a motherboard short on me while doing this mobo was fine just powered off but the fan was a bit funny after

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Post by Riffer » Thu Jan 22, 2009 6:37 pm

I do it all the time when tweaking - including the motherboard ones.

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Post by alecmg » Fri Jan 23, 2009 12:27 am

I managed to kill sys fan speed regulation on motherboard once. Fan and plug worked fine after that.
But hundreds of time there was no ill effect.

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Post by jhhoffma » Fri Jan 23, 2009 7:30 am

I've had systems reset after plugging in a fan. That's enough for me to know that it's not a good idea.

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Post by zoatebix » Fri Jan 23, 2009 9:32 am

Despite my excited sounding "good to hear," I still haven't tried the maneuver.

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Post by Mr Evil » Fri Jan 23, 2009 11:36 am

I think the problem with doing it on motherboard headers is that power to them is supplied via fairly thin tracks, so the sudden surge of current to start a fan may cause a significant drop in voltage. If any other circuitry is supplied from that same track, then it may be affected.

I have frequently done it and not had any problems, but motherboards aren't designed to have things plugged in while they are on.

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Post by sjoukew » Sat Jan 24, 2009 5:14 am

I once short-circuited my psu while connecting a fan. No harm done as far as I know, but I won't hot-plug anymore, just to be sure I don't short circuit anything anymore.

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Post by psymanproductions » Sat Jan 24, 2009 12:46 pm

i do it all the time, id imagine its pretty hard to damege anything by "hot-plugging" fans

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Post by Plekto » Tue Jan 27, 2009 6:46 pm

My fans are set to always be on at specific rpms. Directly wired to the PSU. No problems, ever. Power is power.

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Post by zoatebix » Tue Jan 27, 2009 9:36 pm

Huh. I guess I wasn't as clear as I could have been. Sorry for the confusion, Plekto! I was trying to ask about plugging in fans while the computer is running.

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Post by spcrClox » Tue Feb 03, 2009 7:50 am

I killed 1 (out of 8 or so) expensive odd sized fan on a 1u IBM server by doing this. No big deal you might think but this caused the motherboard to register the fan failure and switch all the other fans into overdrive. Ever heard a plane take off indoors? The joys of 20(?)mm fans at high rpm!
I looked it up and there was tons of people who had done the exact same thing with this same server. Perhaps depending on the design it will be fine, in other times as i (and others) have mentioned, it can go wrong.

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Post by blackworx » Tue Feb 03, 2009 8:24 am

I do the mobo fan header thing all the time, but reading a few of these replies I might be a little more careful in future, especially when working with somebody else's machine.

I've also accidentally shorted a mobo header - not with a fan, but when I was mucking around with a multimeter trying to figure out how the voltage control behaved - and the result was the same as others have posted - instant power-off. I was lucky in that it rebooted fine, but I've read others' reports where they say their whole mobo got fried. I'm guessing the end result might depend mostly on your PSU and the quality of its fault protection.

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