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Case fan voltage mod

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New Member
May 29, 2001
I need to know what size resistor or what size and type if rheostat to get so that I can adjust the case fans to around 7 or 8 volts. Max power is too loud and is overkill and 5 volts is not quite enough. I can connect the stuff easy enough, I just don't know the finer details of figuring out the type of resistor and/or rheostat to use.
You may want to have a variable voltage via a LM317 voltage regulator. You can find them at Radio Shack and the circuit is on the back of the package.
if you just want to run you fan at 7V you can do the 7V trick. just connect the ground(black) wire of the fan to the red wire of the PSU connector and the red wire of the fan to the yellow wire of the PSU. 12-5=7V. if you want to use a rheostat then use R=(12-V)/I. where V is the desired voltage (7V), I is the current rating of the fan(should be on the label) and R will be the value of resistance needed to get 7 volts. you will need a rheostat that will vary from 0 to something close to this value.

oops i mad a mistake on the equation. sorry i did not fix earlier but my isp was down yesterday. i hope this did not cause any trouble.