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Externally powering 2 fans?

By Mugsy ยท 18 replies
Aug 19, 2014
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  1. This is going to sound odd, but I need a way of powering two 120mm exhaust fans in the top of my PC case.

    For some reason, these particular fans keep burning out the power connectors that I plug them into. The fans are not obstructed and spin freely. I don't think replacing them will necessarily fix the issue (though I plan to do that as well). I think it's just "drag" from trying to suck air out of a smallish mid-tower case.

    I need another way of powering these fans (at least until I can figure out why they they keep burning out my plugs). I considered the USB port, but they only output 5v and not enough amps (and last thing I want is to burn out a USB port.).

    Batteries may work, but they'd drain awfully fast.

    Any other ideas? Thx.
  2. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    What do you mean they are burning out your plugs?

    Do they only have the tiny motherboard connector on them and not a molex? The fans shouldn't draw many watts, what fans are they and do they have a power consumption sticker on them?

    I know you want a fix before replacing the fans, but this obviously isn't normal behavior and I'd worry about causing permanent damage to something else. Maybe you should also look into higher CFM intake fan(s) if you suspect they are working too hard drawing (although I really doubt that is the case).
  3. St1ckM4n

    St1ckM4n TS Evangelist Posts: 2,920   +629

    Burning actual plugs???? Either PSU (or mobo if connected to mobo) or fan is faulty, find out which. This is dangerous.
  4. Mugsy

    Mugsy TS Guru Topic Starter Posts: 394   +15

    Sorry for the super-late reply. Replies from this site were being flagged as spam. :(

    I first plugged my fans into one of the 3-pin fan connectors on my motherboard. This worked for about two-three months when I suddenly noticed they weren't working. For how long, I have no idea because they were covered (case top dust cover.)

    So I plugged them directly into my psu using a Molex-to-3pin adapter. Again, two months later, they stopped working. I removed the vented case top as a reminder to fix the fans at a later date, and suddenly a couple of days later, the fans started working again on their own (as long as they remained uncovered).

    This lasted about a month before they stopped again. Again, the power connecter they were plugged into is now dead.

    So I hooked one of the fans (12v 0.2amps) up to some D-cell batteries (7.5volts worth) and that's how I'm powering one (of the two) exhaust fans right now.

    If the fans can be driven by just a few D-cell batteries all day, they can't possibly be drawing that much power to burn out two different power connectors.

    I'm stumped. :(
  5. St1ckM4n

    St1ckM4n TS Evangelist Posts: 2,920   +629

    How are the fans stopping from a bit of dust? I'd wager that they are faulty.
  6. Mugsy

    Mugsy TS Guru Topic Starter Posts: 394   +15

    Who said "dust" was stopping the fans? The fans are not faulty. They spin freely and are being powered at this very moment by a series of D-batteries.
  7. St1ckM4n

    St1ckM4n TS Evangelist Posts: 2,920   +629

    Alright, I misunderstood this:
    I still say they are faulty. Mobo and molex connectors both caused the fans to randomly stop working? Unlikely.
  8. Mugsy

    Mugsy TS Guru Topic Starter Posts: 394   +15

    How can I verify if the fans are faulty before wasting money replacing two fans that work fine on DC power?
  9. mr.simonski

    mr.simonski Banned

    They burn the plugs? Wow, I never heard of something like that before.. I would suggest to use an second external power supplier and run the fans on that one. If they don't fail during a week or so it's your mainboard, not the fans.
  10. Mugsy

    Mugsy TS Guru Topic Starter Posts: 394   +15

    Not "burn", "burnout", as in "blown fuse" and no longer putting out power.
  11. mr.simonski

    mr.simonski Banned

    Oh, excuse my bad english understanding :)

    It still sounds interesting that two fans use so much ampere that they burnout some part of your mainboard. Normally the fan connectors offer 5V or 12V with at least 600mA, sometimes 1A - isn't that sufficient?
  12. Mugsy

    Mugsy TS Guru Topic Starter Posts: 394   +15

    The fans are rated @ 12v 0.2amps. I am currently running just one fan using a series of 5 D-cell batteries (7.5v total), so they clearly don't need a lot of power to run.

    Motherboard: Gigabyte Z87X UD4H
    PSU: Thermaltake 750watt modular power supply.
  13. St1ckM4n

    St1ckM4n TS Evangelist Posts: 2,920   +629

    Use multimeter to test maybe?
  14. Mugsy

    Mugsy TS Guru Topic Starter Posts: 394   +15

    Did. Connected to the batteries, the fan fluctuates between 4v-6v.

    I think I'm going to purchase a pair of "bearingless" fans and see what happens (the hard part will be finding a free molex connector that still works.)
  15. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    A lot of the fans with molex connectors are 'pass through' connectors, so you don't end up losing any.
  16. mr.simonski

    mr.simonski Banned

    It still sounds very unusual that a fan can burnout your molex connector plugs. I would get a new fan as I would be afraid of damaging my motherboard by using those fans.
  17. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    That doesn't make any sense. The molex connectors have nothing to do with the motherboard, only the PSU.

    I suggested new fans in the first reply, and everybody, including Mugsy is on board with the new fans idea.
  18. mr.simonski

    mr.simonski Banned

    As the molex connector is part of the PSU and the PSU is connected to the mainboard there is of course the risk you will brick your mainboard when the PSU was broken by the fan.

    Two months ago the PSU of my desktop PC started burning, the whole apartment was smelling like burned plastic. It was hard to get the smell out of the room. So maybe I'm a bit too careful with such things right now.
  19. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,729   +409

    Perhaps if you have a $20 700W PSU. Any even halfway decent PSU will not take a large drain on one 12V rail and destroy the motherboard in the process. You often hear about people having stability problems running a high powered video card on an underpowered PSU. That puts a lot of stress on the PSU and the game crashes, OS locks up, or computer reboots - how many times is the motherboard fried when that happens? Almost never (I'd say never, but I'm sure you could come up with an example with enough web searching).

    Point is - replacing the fans was encouraged early on in the thread, and we discovered nothing was 'burning' or melting. It is almost certainly a problem in the fan itself with a connection, and that nothing is shorting out - I imagine if you short a molex connector on a running PC right now, everything will shut down.

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