CPU fan error

[Rextus]

Hello all,
I burnt an old thermal speed controlled fan (wups) and with my amazing soldering skills, I have connected an old Intel fan to the what looks like an OEM plug onto the mobo. It is a 3 pin CPU connector with a shroud around the 3 pins. The 3 wires are red, black, and yellow. I connected the yellow wire from the Intel fan to red of the plug, and black with black. Yellow from the plug isn't connected, so are the green and blue wires from the Intel fan. Upon startup, the fan turns at max speed, which doesn't bother me much, but after POST, there is an error message stating:
"Alert! Previous fan failure
Strike the F1 key to continue, F2 to run the setup utility"

Striking F1 starts Windows XP no problem.
The problem is that I am planning to give this computer to my very technophobic neighbor, and I know that she will not even bother to read the error message before trashing the desktop. So if anyone know how to solve this, please consider helping me.

Thanks in advance!

P.S.: I know the loose yellow wire is to blame, but I don't know where to connect it and that is my last Intel fan, so I don't want to blow it.

 

[Paperdoc]

I'm guessing the fan has 4 wires coming from it, in the order Black, Yellow, Green, Blue. That is the standard 4-pin fan color code. Then the connector you soldered onto the end of those wires is a standard 3-pin fan connector with wires in the order Black, Red, Yellow. You got the first two correct: Blacks together are Ground; Yellow from fan goes to Red from 3-pin connector for the +DCV Supply. What you need then is to connect the GREEN from the fan (for Pin #3) to the YELLOW from the 3-pin connector's Pin #3. That line is the speed signal generated by the fan and being sent back to the mobo header. The fan's Blue wire connects to nothing. This will ensure that the speed signal reaches the mobo and will stop it from sending out a fan failure alarm.

Wired this way the fan can only receive the standard signals from a mobo fan header that is using Voltage Control Mode (aka DC Mode), and cannot receive a PWM signal from Pin #4 (the Blue wire) that is not connected. Right now you say the fan runs at full speed constantly, which is what any fan will do IF its header is using PWM Mode as the control method but the PWM signal is not reaching the fan. Look in BIOS Setup for the fan header you have this plugged into. See if there is an option to change that to use DC Mode or Voltage Control Mode. If you find that and make the change, remember to SAVE and EXIT, which will reboot the machine and remember that setting. If that is done, the mobo CAN control the speed of this fan. 4-pin fans have a backwards compatibility feature that allows them to run under speed control when fed by a 3-pin header using Voltage Control Mode.

 

[Rextus]

I'm guessing the fan has 4 wires coming from it, in the order Black, Yellow, Green, Blue. That is the standard 4-pin fan color code. Then the connector you soldered onto the end of those wires is a standard 3-pin fan connector with wires in the order Black, Red, Yellow. You got the first two correct: Blacks together are Ground; Yellow from fan goes to Red from 3-pin connector for the +DCV Supply. What you need then is to connect the GREEN from the fan (for Pin #3) to the YELLOW from the 3-pin connector's Pin #3. That line is the speed signal generated by the fan and being sent back to the mobo header. The fan's Blue wire connects to nothing. This will ensure that the speed signal reaches the mobo and will stop it from sending out a fan failure alarm.

Wired this way the fan can only receive the standard signals from a mobo fan header that is using Voltage Control Mode (aka DC Mode), and cannot receive a PWM signal from Pin #4 (the Blue wire) that is not connected. Right now you say the fan runs at full speed constantly, which is what any fan will do IF its header is using PWM Mode as the control method but the PWM signal is not reaching the fan. Look in BIOS Setup for the fan header you have this plugged into. See if there is an option to change that to use DC Mode or Voltage Control Mode. If you find that and make the change, remember to SAVE and EXIT, which will reboot the machine and remember that setting. If that is done, the mobo CAN control the speed of this fan. 4-pin fans have a backwards compatibility feature that allows them to run under speed control when fed by a 3-pin header using Voltage Control Mode.

Nice, I will try it later next week. I always though that PWM signal need 2 wires to control the "pulse". And no, my mobo is really old and basically has no advanced options, so there goes that.

 

[Paperdoc]

Post back here the maker and exact model number of your mobo, and I'll look at its manual for hints.

Thanks for Best Solution.