cpu fan connection not working, but the fan does.

[JCROCCO]

The CPU fan is connected to the mobo at the cpu fan connector, but it is not working. I switched fans, and it didnt work. I put the fan on the system fan connector and it works.

What can cause the cpu fan connector, not fan, to stop working? Can I use the system fan connection for the cpu fan? The wires are too short to reach, but I can take the connector from an old fan and splice them to get the length needed to work.

I dont know if there is a difference in the way the system and the cpu fan work. My system has been unstable for a week now, freezing and locking up. Can that do real damage to the CPU or does locking it up prevent damage?

 

[Zap]

Your CPU overheating may cause instability. Possible, but unlikely that it is damaged. What CPU is it? Anyways, it usually doesn't matter how you power the fan. The only thing is that some boards do special monitoring or speed controlling of the fan header marked for CPU.

Have you checked to make sure Smart Fan setting in BIOS isn't shutting off the fan?

 

[JCROCCO]

There doesnt seem to be a setting for that. it is a socket 478 P4 2.8. The bios just shows the fan speeds, and the system fan was running, the cpu fan was not. I let it run with a secondary fan plugged into the cpu fan port and watched, it never came on, then the system froze.

What could cause the system fan port to just stop working?

 

[fluffedup]

I've managed to fry a fan header. Not one of my finer moments, but I was messing around with something or another inside the case while the computer was running. Full Disclaimer: I was using a screwdriver to do this messing around. The screwdriver accidentally touched down somewhere on the board, the computer shutdown, then I smelled and saw the magic smoke. I was afraid I did some serious damage to, well, everything, but it turned out that the only casualties were the two uppermost fan plugs, one of which being the CPU fan header.

All that said, you can run a CPU fan off of the "system fan" connector. You may lose some of the fan speed control functions. I had a socket 478 board that only allowed slowing down the CPU fan header, so it may be louder than you expect. SpeedFan or some other fan control program may still work, though.

Make sure that you turn off any "Warn on fan failure" features in the BIOS. For the board with the headers I fried, when I turned it on with the CPU fan in the "system fan" header, it made an awful siren sound immediately upon startup and automatically shut itself down after 30 seconds because it was reading that CPU fan was 0. I turned off the CPU fanspeed warning and "shutdown on fan failure," and I was good to go (it's been 5+ months).

The board I fried was a 775.

I'm not sure what would cause a header to spontaneously stop working other than maybe a grounding problem or a seriously messed up fan, but it sounds like your fan is fine.

Like the person above me said, you're not likely to damage your processor running it like this; I'd assume it's just reaching a limit temperature, then shutting off. I doubt it's damaging anything, but I can't imagine it's necessarily good for the system. If you get the fan working on an alternate header, I'd keep the CPU temperature warnings and shutdown conditions turned on in your BIOS, but disable the CPU fan header controls.

 

[imported_wired247]

definitely could've fried a header.


plug it into the system fan connector but be cognizant of whether or not the fan is working. if it stops working your CPU will probably still chug along, but your computer will be unbearably slow.


through many startups and shutdowns over the years, startups in particular pull a lot of current. some older mobos simply don't have the most robust fan headers. If your fan was a bit dusty or the bearings were getting worn out, it could've pulled a little too much current.