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I have a 120mm Rosewill in the front of my case for intake. I want to run it at its max 12V when gaming and then 5V for everything else. I have a toggle switch that's made for a car:



I know "earth" is ground, supply is the power source and load is the object the power is powering, but can i run the fan at 5V and then turn the 12V circuit on with the switch? Or will it add both and make it 17V or will the higher voltage just take over?

Diagram:



If this won't work, then can I just use the yellow 12V circuit with the switch and turn the fan off or run on 12V as my only options?

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Is the fan a 3-pin fan and you're attaching an adapter to the end of it? You can't assume that the yellow fan wire is the same as the yellow PSU wire. The yellow fan wire is an RPM signal. (http://www.allpinouts.org/index.php/..._Fan_Connector)

If you have a multimeter, you should ohm out the switch to find out how it works (since there's some confusion over that). If it simply switches two inputs into one output then it will work.

For a switch that controls the fan between 5V and 12V, follow the diagram I attached.
LL
 

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Discussion Starter #3
Quote:

Originally Posted by spartacus View Post
Is the fan a 3-pin fan and you're attaching an adapter to the end of it? You can't assume that the yellow fan wire is the same as the yellow PSU wire. The yellow fan wire is an RPM signal. (http://www.allpinouts.org/index.php/..._Fan_Connector)

If you have a multimeter, you should ohm out the switch to find out how it works (since there's some confusion over that). If it simply switches two inputs into one output then it will work.

For a switch that controls the fan between 5V and 12V, follow the diagram I attached.
yes the 3to 4 pin is the adapter it came with to connect it to a molex instead of the mobo.

i guess i hadn't noticed that the yellow wires for fans and psu are different b/c if i look where the molex connector connecst to the yellow wire on the psu, it ends up going through the red wire of the fan, so i guess you're right.

the switch i have is a rocker switch. i tested it with a digital multimeter and i believe it is just a basic on/off switch (connected black to load and red to supply).

so what would i do in this case?

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Discussion Starter #4
ok this is how i got the switch to turn the fan on/off:



i believe the "earth" is for grounding the led b/c the led doesn't go on when i use the switch (idc though, it won't be visible).

what i wan't to know is if it is possible to run it 5 volts constantly and then when activating the switch, having the 12volt enable. but will that turn into 17volts or will the 12 volt just "takeover" the 5volt?

 
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