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Fan volt help

F

Firebomb

[H]ard|Gawd
Joined
Jul 21, 2002
Messages
1,692
I have a fan that is really to loud... and what im doing is modding it so its not so loud. it runs less cfm yes but I was wondering could it cause damage to fan or anything.?

what im doing is, taking the 4 pin power with switch and turning it into 2 wire aka the yellow and black. this makes it like 7 volt I think. not really sure. but It makes it hella quiet.

It means that the fan is given a reduced voltage to slow it down (and quiet it down). It's usually done by grounding the fan to the power supply's +5V line instead of to a ground wire, which reduces the effective voltage to (12 - 5) = 7 volts.

any ideas? can it hurt me?
 
The yellow wire is actually +12v, so I find it a little strange that your fan actually changed its speed. The red wire is 5v, so you'd want to use that one to slow down the fan, or use the other method of grounding to +5v to get an effective 7v of power. However, your current method should be supplying the full 12v to the fan.

Also, no, removing two of the molex wires won't hurt you. Generally, fans with molex connectors only have pins for the yellow and one of the black wires.
 
Just to clarify

to run a fan on 7V you connect the + wire of the fan (normally red and wanting 12V ) to the YELLOW (+12V) wire of a normal PC power supply and you connect the - wire (normally black and wanting ground/0V) of the fan to the RED (+5V) wire of a normal PC power supply. This give the fan a potential voltage difference of 7 V. ( +12 - +5 = +7)

The confusion comes about because most fans have a red wire as the postive 12V lead (assuming it is a 12 volt fan). The red color on the fan wire does NOT indicate voltage, it indicates polarity only, a red fan wire just means that wire is the postive + wire.

PC power supplies DO use a color code for the wires that indicates voltage. YELLOW is +12 RED is +5.

Red to Red and Black to Black will run your fan at 5V, if it will run at all.

Look closely at your prewired fans that use a molex 4 pin connector. you will see that the red wire from the fan on the fan side of the connector gets connected to the yellow wire on the pc power supply molex.
 
If I remember correctly, running your fan with the 7V hack puts undo stress on the PSU rail as well. I think you're supposed to close the line by plugging the next molex into a CD-ROM or similar device. Could someone with more knowledge help out here?
 
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