Question Front case fan randomly whirls up

[NinCollin]

I've got this dual Xeon PC with a couple of quirks, but is otherwise functional. One of those quirks is with the front case fan.
This PC has four 4-pin fans, and the fan for the front case randomly speeds up drastically for ~3 seconds every now and then. The temperatures aren't crazy and are pretty stable (it happens even when doing nothing, even when sitting in the BIOS.)

The issue persists after swapping the side fan with the front fan, so it's not necessarily the fan to blame.

My only three theories are as follows

• The motherboard is damaged and sending too high of a fan speed for no reason
• The type of fan used has a limited range of settable speeds that causes its speed to spike
• The motherboard is working and is intentionally sending out a crazy speed

When the fan whirls up, it's RPM jumps up ~1000. I plugged in a different type of fan from a box I had, and while it didn't appear to have this issue, I was not monitoring it's RPM to see if it jumped.

 

[lvt]

For the front case fan, you can use a regular 3-pin fan instead so that the fan speed will remain constant.

 

[Paperdoc]

Since this happens with two different (but similar) fans, it appears the header is doing this. However, there is another possibility IF these are 4-pin fans. With that fan design IF the PWM signal from header Pin #4 does not get through, the fan will go to full speed to ensure you DO get cooling. So maybe the connection for that signal is intermittent. Try this. For that front fan header, unplug it and re-connect it. Do this several times. While you're at it, check that the pins of the header are firmly in place, and inspect the connector on the end of the fan's wires to be sure the connections inside that seem secure. Re-connect and see if that makes any difference. The unplug - replug repeat action MAY "scrub" a little oxidation off the contacts to clean them.

 

[NinCollin]

Since this happens with two different (but similar) fans, it appears the header is doing this. However, there is another possibility IF these are 4-pin fans. With that fan design IF the PWM signal from header Pin #4 does not get through, the fan will go to full speed to ensure you DO get cooling. So maybe the connection for that signal is intermittent. Try this. For that front fan header, unplug it and re-connect it. Do this several times. While you're at it, check that the pins of the header are firmly in place, and inspect the connector on the end of the fan's wires to be sure the connections inside that seem secure. Re-connect and see if that makes any difference. The unplug - replug repeat action MAY "scrub" a little oxidation off the contacts to clean them.

Amazingly, you might be onto something

It kept whirling (even with a completely different fan) but after playing around with partially connecting the fan and reconnecting it, it's been whirl free for a bit now

It might not last though, but so far so good
I guess that explains why it didn't seem to start till the second day I got this machine


However, it seems very finicky; simply picking up the PC and moving it back to my shelf was enough to undo the perfect position it was in. I definitely need to inspect the connectors further and see if maybe the header can be cleaned. It definitely can work though, so it's at least hopeful. If all else fails, I can just wiggle the fan connector anytime I move the machine until it stops whirling.