Fan wiring

[Firewall]

Hey guys, I was wondering if you could help with some wiring. I have the CPU fan off and it has 4 wires, red, black, yellow, and blue.

I want to replace it with a bigger fan (80 mill) but the one I have here only has 2 wires, red and black.

I know the reds and blacks are for power and ground so I have to assume the blue and yellow on the smaller cpu fan are for controlling the RPM's.

I want to know If I cut the adapters off of both fans, what wires I am going to have to splice so I , or rather the software, can change the RPM's on the 80 mill fan.

I know it's black to black and red to red but that leaves me with nothing for the blue and yellow. Am I out of luck?

 

[DermicSavage]

The yellow wire is the RPM sensor, it does not control the RPMs of the fan itself(this is controlled by the voltage fed into the fan).

As a side note, the blue wire is for the thermal sensor I belive(some dells and new P4s have them)

 

[Firewall]

I've got a p4 so that explains that, so is there any way I can splice these into the red wire to get it to work on the bigger fan?

I think I already know the answer...

 

[DermicSavage]

You do not need the RPM or Temp sensor to have the fan work. Plug it in and use it

EDIT: assuming your system isnt a propreitary OEM peice of trash(I know dell has proprietary fan wiring for the 478 P4s), it wont need either of those wires.

 

[Firewall]

I know, but I'm sick of my pc sounding like a jet engine. the way I have it set up now is the cpu fan is in the front of the pc pulling air out. The rpm's change when the temp changes. Obviously this doesn't matter because it isn't on the cpu.

I have an 80 that is on my radiator that is constantly on high. I want to wire that 80 so when the computer is cool it will spin slower so it won't sound like an airport in my room.

I'm on ebay now and I see 3 pin 80 mm fans but I need 4 pin...

 

[DermicSavage]

If your fan is plugged into a molex from the power supply, youre out of luck.(soem power supplied have special molex connectors that feed 5v instead of 12v through those wiress though)

If the fan is plugged into the mobo, there might be an application that can control the voltage going to that fan. I dont know any programs that do that, but speedfan might(havent used it, but it does a lot of stuff)

And once again, the RPM sensor wire is for the RPM SENSOR, it does NOT control the fan speed

 

[Firewall]

If your fan is plugged into a molex from the power supply, youre out of luck.(soem power supplied have special molex connectors that feed 5v instead of 12v through those wiress though)

If the fan is plugged into the mobo, there might be an application that can control the voltage going to that fan. I dont know any programs that do that, but speedfan might(havent used it, but it does a lot of stuff)

And once again, the RPM sensor wire is for the RPM SENSOR, it does NOT control the fan speed

I see what you are saying now. So, if I just hook up the black and red wires my sillentek will still make it go faster or slower through the voltage, but it just won't report the rpm speed to me. Is this right?

 

[DermicSavage]

correct

 

[Javelin3o4]

yeah some oem systems need to sense the rpm from the cpu fan or everytime you boot it will give you a cpu fan failure message. and some systems dont have an option to disable cpu fan monitoring.

 

[Firewall]

yeah some oem systems need to sense the rpm from the cpu fan or everytime you boot it will give you a cpu fan failure message. and some systems dont have an option to disable cpu fan monitoring.

I have an aopen mobo and the fan came with my cooler masters case I think.