Really odd PC fan activity

So, this is odd. I've built many computers, but this is a first.

I have a computer that I put together three years ago, that I built using an Antec case that came with a stock Antec 500w 80+ power supply and a stock 120mm case fan. I (for odd reasons) ended up with an aftermarket 550w 80+ power supply that I decided I should swap out. Why? Well, the new supply has one of those big fans that points down, and it doesn't work with another computer I am working on. The existing power supply has an 80mm fan that points out the back, which I could use in the new computer (rack mount, hopefully).

So I made the switch. Now, at odd times, my computer freezes up when I wake it from sleep. And my case fan (NOT the power supply, and NOT the cpu fan) slowly starts speeding up. It sounds like it's going to explode. Speed fan tells me it gets up to like 10k rpm! Normally it's somewhere around 3k! Honestly, it sounds like a bomb in a movie right before the building explodes. But then...Windows starts working normally...and the fan slowly starts...slowing down. I don't know if this has anything to do with the new power supply, but I haven't changed anything else.

Thoughts?

Reply 1 : Really odd PC fan activity

When a PC starts to hibernate it will shutdown or idle the PC. This in turn shuts the fan(s) one by one or all, except maybe the PSU. When it wakes-up because it was stewing in its own heat bath, it senses the temp change and quickly throttles-up and that means RPMs. The greater RPM is allowing the PC to catch-up to a safe cool level and proceed which is normal. Make sure the new PSU fan is working right. I'm sure the fan pointing down is really sucking out the hot air, rather than blwing down. Though, that could be very possible as such setups are made that way to directly help cool the cpu. However, the freeze maybe a response to safe-guard the PC or is shutting down in order to save itself. This could also be part of ACPI or power modes. You need to recheck everything in the bios and/or your setup and play with it. You may need to check the fan ordination as well because once a change is made, while minor is a major factor in some aspects. I can't make a definite answer as too many factors make a PC work now and custom PCs just add to this, only a hands-on and observation plus trial&error may make it settle down to your liking.

tada -----Willy

Reply 2 : Really odd PC fan activity

Thanks Willy! This makes sense, except for one thing: my setup doesn't hibernate on it's own...I have a button on the keyboard that can send the computer into hibernation. However, the problem arises when the computer has gone to sleep. This happens when the system goes idle, the monitor goes into power saving mode, and...well, actually, I'm not even sure what happens to the computer then! Once one move the mouse or hits the keyboard, the monitor comes back on, and then the problem begins.

I will recheck everything, like you suggested. As for the orientation of the power supply fan, I was under the impression that ATX psus can only be installed one way, and the placement of the screws ensures that. LOL, it's a mess!

Reply 3 : Really odd PC fan activity

If you have various or any USB devices attached when this happens that can cause issues or rather you need to wait until it clears itself. The more devices, the more time involved, which is why i mentioned the setup various and it boils down to what you have. Sleep, hibernate, i don't differentiate, though others can, it really is basically the same thing. Also, the topic itself has been discussed before. Sometimes, the real fix is to get a similar PSU like you're older one and hopefully a larger wattage unit and leave it at that. I can't tell from here all your details, but regardless it again needs you to pay attention to details AND WHAT MAY WORK best. I leave out any updates, OS issues, older USb devices, etc., I'll take nothing for granted.

tada -----Willy

Reply 4 : Really odd PC fan activity

machine, fans with speed controls from MB input would start up running fast and slow down once Windows was up and running. If I halted the boot process and checked the temperature posted in the BIOS, it was much higher than the ASUS PC Probe would report after Windows loaded. The temperature would slowly come down. This was a dual boot machine with on HD running XP and the other running Win 2K. When I'd run Win 2K, PC Probe would report the higher temperature and show the fans at higher RPM. Some research I did suggested that XP was much better at handling power usage...whatever that's supposed to mean. Because I got different temperature values on the same machine depending on which drive I'd boot from, I believe the XP information was correct. The machine would run very hot and fans would turn fast when I'd interrupt the boot process and stay in BIOS screens and things would cool off once XP finished loading. Some sort of magic, I guess.