Can I safely rewire molex fans?

William

New member
I want to permanently* reduce speed of some molex case fans (2x 120, 1x 80). I have them connected on a single PSU wire in a queue one after the other.

I think that the best way would be to switch wires (12V for 5V) on the first molex which would change the whole queue to be powered by 5V and therefore reduce their speeds. I already did this on a one testing fan and old PSU (started up using paper clip on green and black wires) and it was working.

And finally to my question. Can I safely use it this way? I am mostly concerned about PSU, I don't want it to get damaged because draining 5V without 12V or something like that. I think it should not cause any problems but just to be safe I wanted to ask you guys since you know much more about computer hardware than I do.

* Better to say until I decide otherwise which won't happen sooner than in summer.
 
Well modern quality PSUs will be fine, however if you want to be on the safe side, add something to absorb the extra power. ODD etc would be fine.
 
Thank you for the response, but I have a question. What does ODD mean? Do you mean something like old DVD burner? I have one molex burner lying around that I could install to the case.

Would it be enough if it was just connected (ready for use - stand by mode) and not used? I guess I should connect it on the previous molex connector from the same wire branch so it would not be affected by this change. Am I right?
 
You could rewire the PSU molex sockets but IMHO id just get some reducers they are extremely cheap and usually come in packs of 3 or 5.

I use these.
7bFLL3i.jpg


But you can get molex reducers too in 5v or 7v variants. They are probably the best way to go if you are concerned about the safety of your PSU.
 
Thank you for the suggestion. From the screenshot of those molex reducers I judge that it is pretty much what I was doing in that testing environment.

Does those on the screenshot have resistor under that black protection? That could be an interesting (probably safer) solution as well.
 
I am mostly concerned about PSU, I don't want it to get damaged because draining 5V without 12V or something like that.

:eek:

..if you want to be on the safe side, add something to absorb the extra power.

:mellow:

That could be an interesting (probably safer) solution as well.

:confused:

You could also just run a 1 to 3 Y cable with the reducer if you cant find any 3 packs.

:unsure:


This is probably the sketchiest advice i've seen in a while. You definitely won't 'underload' a 12v rail by missing off a couple of fans and I very much doubt you will overload the 5v, but of course check your PSU rating for each rail.

Modifying the molex to fan adapters by moving the +12v into the +5v is really the easiest, simplest and safest way to do what your trying to do. The power draw of a fan is so insignificant it won't affect your PSU. The only risk might be if it's not enough for the fans to start spinning. But of course you've tested that already.

Using a splitter cable with a single resistor really isn't a great idea, the resistors are specced appropriately for a single fan not 3. The original idea is fine, if the fans run fine at 5v then go with that.

JR
 
You could also just run a 1 to 3 Y cable with the reducer if you cant find any 3 packs.
I am sorry but I don't understand what does it mean. I am not that "skilled" in computer hardware.

@JR23
It looks like you know what you're talking about. Can you please tell me what should I look for in PSU manual?

Did you mean this?
+5V ... Imin 0.2A, Imax 15A
+12V ... Imin 0.1A, Imax 37A
 
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