Replacing Fans

Blue_Sky · Post by **Blue_Sky** » Wed Jun 20, 2007 9:21 am

Hi everyone,
Searching the forums here nor google have resulted in an answer to this question:
Am I going to be able to replace a two pin motherboard fan and a two wire PSU fan with fans that have three pin motherboard connectors and molex connectors?

I assume that I can cut off the the two pin connector and replace the three pin connector for the motherboard (or just not bother and use the molex connector) and that I can connect the two PSU wires to the right molex pins (or again should I just use up another molex connection).
It all just boils down to: is the mobo or PSU going to freak out at some point if there are no fans attached to where they normally should be?

Thanks,
Blue

Post by **NeilBlanchard** » Wed Jun 20, 2007 10:23 am

Hello,

The third (yellow) wire is the tachometer signal, and it there for monitoring only. Not connecting it should not affect the fan at all. You just have to get the other two wires connected with the correct polarity (match color to color).

Blue_Sky · Post by **Blue_Sky** » Wed Jun 20, 2007 10:47 am

I guess I wasn't very clear. I know how to do both replacements (it will probably be as simple as swapping the old fans out and plugging the new ones into molex connectors). I'm just not sure whether the motherboard is going to give me some sort of error if it does not detect a fan (same with the PSU really - will it refuse to start up, or shut down when it hits a certain temp?). I just really have no clue, as I've always used laptops.

Thanks for the reply.

jaganath · Post by **jaganath** » Wed Jun 20, 2007 10:50 am

Some motherboards will halt the POST process if a CPU fan is not detected or the fan RPM is too low. AFAIAA no PSUs have this feature. The only way to know is to try. If the motherboard does freak out there are ways round it.

charred_water · Post by **charred_water** » Wed Aug 01, 2007 2:14 pm

I replaced the 92mm Dell fan cooling my P4 in my Dell Precision 330 with a Nexus fan. I connected the Nexus to PSU molex connector whereas the Dell fan was connected to proprietary Dell 3 pin connector on motherboard. The Dell fan seems to have temperature sensor built into fan.

When I reboot, the BIOS complains "no system fan detected, press F1 to continue". My system boots normally if I press F1.

Is there a workaround for this? Can I plug the Dell fan plug into the motherboard and somehow fool the BIOS into thinking the system fan is connected so I don't have to press F1 to boot?

Post by **NeilBlanchard** » Wed Aug 01, 2007 6:03 pm

Hello,

If the BIOS has a setting to ignore the CPU fan -- then that would fix it. Asus has this, and they make a lot of Dell mobo's (I think), but the BIOS may be "cut down"?

stromgald · Post by **stromgald** » Thu Aug 02, 2007 8:53 am

charred_water wrote:Is there a workaround for this? Can I plug the Dell fan plug into the motherboard and somehow fool the BIOS into thinking the system fan is connected so I don't have to press F1 to boot?

I was never able to fix that problem on my Dell Dimension 8200. I had replaced the original fan with an Arctic Cooling cooler which had a 3-pin connector. The fan just didn't go as fast as the old one and 75% of the time I boot up, I have to hit F1. Maybe your BIOS is different, but I've just learned live with the minor annoyance.

charred_water · Post by **charred_water** » Fri Aug 03, 2007 8:50 am

There is some good advice about fixing this problem in this thread:
viewtopic.php?p=358865#358865