5 volt 4-pin molex doesn't completely work

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dan
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5 volt 4-pin molex doesn't completely work

Post by dan » Sun Mar 04, 2018 4:44 pm

i have a corsair case with 3 front fans with blue led and a top 20cm fan (i think) all use the old legacy 4 pin legacy.

there are 3 such fans and my own 2-pin 120mm fan, the 3 fans each have a 4-pin with a pass through

using a pass through molex 4-pin with 3-pin fan connector i connect 2-pin 120mm fan

using a pair of pliers i cut throught he very hard plastic and then reversed the connection on the power molex from PSU a corsair PSU to fans, from power to the first one, but the other 2 are normal.

now the 2-pin 120mm fan works fine, it whirs and is almost silent.

the led fanlights up very dim but visible

but none of the 3 case fans are running.

at normal 4-pin molex alignment it works but too noisy for my taste.

can this be made to work somehow?

Olle P
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Location: Sweden

Re: 5 volt 4-pin molex doesn't completely work

Post by Olle P » Tue Mar 06, 2018 12:09 am

dan wrote:using a pair of pliers i cut throught he very hard plastic and then reversed the connection on the power molex from PSU a corsair PSU to fans, from power to the first one, but the other 2 are normal.
This I have difficulties to envision.
Can you provide a picture or drawing of the cable arrangement?

dan
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Joined: Sun Jan 25, 2004 2:01 am
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Re: 5 volt 4-pin molex doesn't completely work

Post by dan » Tue Mar 06, 2018 8:40 am

Olle P wrote:
dan wrote:using a pair of pliers i cut throught he very hard plastic and then reversed the connection on the power molex from PSU a corsair PSU to fans, from power to the first one, but the other 2 are normal.
This I have difficulties to envision.
Can you provide a picture or drawing of the cable arrangement?

sure!

i take this

Image


i cut incisions into the plastic

turn it upside down

connect with this
Image

5 volts this way, LED light up but fans don't whirr and spin

dan
Posts: 1243
Joined: Sun Jan 25, 2004 2:01 am
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Re: 5 volt 4-pin molex doesn't completely work

Post by dan » Tue Mar 06, 2018 8:43 am

everytime i post here i get this


Error 524 Ray ID: 3f761af324307ad0 • 2018-03-06 16:14:20 UTC
A timeout occurred

Olle P
Posts: 711
Joined: Tue Nov 04, 2008 6:03 am
Location: Sweden

Re: 5 volt 4-pin molex doesn't completely work

Post by Olle P » Wed Mar 07, 2018 7:25 am

Ignore the timeout and just close the tab after hitting "submit".

Your pictures don't show how the cables are drawn between the connectors/pins, which is my concern.

dan
Posts: 1243
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Re: 5 volt 4-pin molex doesn't completely work

Post by dan » Wed Mar 07, 2018 8:00 am

Olle P wrote:Ignore the timeout and just close the tab after hitting "submit".

Your pictures don't show how the cables are drawn between the connectors/pins, which is my concern.
i just turn it upside down and plug it in, to get it to fit i cut incisions into the plastic,

Olle P
Posts: 711
Joined: Tue Nov 04, 2008 6:03 am
Location: Sweden

Re: 5 volt 4-pin molex doesn't completely work

Post by Olle P » Wed Mar 14, 2018 4:47 am

Now I think I understand:
You're essentially feeding 5V on the 12V input and 12V on the 5V input on the fans.
Then the problem can be assumed to stem from having 12V on the 5V line, causing problems with some regulator.

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