Air Ventilation Problem! Please Help!!

Jan 26, 2014
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Whenever I put the side panel on my case all of the fans rev up like a vacuum cleaner and my CPUs temp goes up like crazy! How do I fix this problem?! If I need to I can take a picture of my system and show it to you guys. My Asus motherboard also says I have a cpu fan error whenever I boot as well? Does anyone have any ideas?
 

Paperdoc

Polypheme
Ambassador
First problem first: the fans speed up when case is closed. Surely this means there is not sufficient air flow though your case, most likely because there is not sufficient air intake. So, how are your fans set up? How many intake fans are there, and where in the case are they? How many exhaust fans, and where? Have you checked the foam filters on the intakes to see if they are clogged with dust?

Second problem: CPU Fan Error. Most mobos monitor the CPU cooling fan carefully and warn you if it fails. Some just warn you, some put out alarm beeps, some even shut down the entire machine without even waiting for the CPU to overheat. Apparently, yours just does the warning thing, so it is up to you to investigate and fix this.

Now, what can cause this alarm?
1. A real fan failure. IF you have your CPU cooling fan plugged into the mobo's CPU_FAN port, open the case and turn on the computer. Observe the CPU cooling fan immediately. Does it start up right away? Normally it should start up very fast, then slow down in a few seconds. It should ALWAYS run. If it is not running, or if it seems only to run very slowly, it may be worn out (its bearings, usually) and need to be replaced.

2. Good fan performance and connections, but a poor setting in BIOS Setup. In BIOS Setup some mobos allow you to set the minimum acceptable CPU fan speed. But some fans are very good at moving air even at low fan speeds (especially when the fan slows down slightly a few seconds after startup, because the CPU is still cool), and although the fan is working properly and cooling the CPU, the BIOS thinks it is running too slow. Look up specs for your CPU fan, and check what the actual CPU temperature is at low processing loads ("idle") and when very busy. Compare those temps to specs for the CPU. If you are getting good cooling, maybe you just need to lower the alarm level setting in BIOS to eliminate this false "error".

3. A bad connection where the fan plugs into the mobo's CPU_FAN port. The fan generates a speed signal as two pulses per revolution and sends it back to the mobo on Pin 3 of the port. The mobo counts those pulses to measure fan speed. If the connection for Pin 3 is dirty that signal may not get to the mobo reliably, and the mobo falsely believes the fan is not spinning right. OR, a dirty connection on either Pin 1 or 2 might really limit the electrical supply to the fan motor and cause it to run slower than it should. In either case, you could try a simple procedure. With the computer shut down, open up the case. Carefully unplug the CPU fan from its mobo port, then plug it back in. Do this several times. Then CHECK to make sure you did not disturb something else and disconnect it. Close up and turn on. Did that help? This process can scrub clean the contacts of the connector.

4. CPU Fan NOT connected to the CPU_FAN mobo port. This has two sub-variants. In BOTH cases, the result is that the CPU fan's speed pulse signal is not getting to the CPU_FAN port Pin3, so the mobo believes that this fan is not working at all.
4 (a): you have your CPU fan plugged into the wrong mobo port. So, although the fan is working, its speed signal is not getting to the correct port to read.
4 (b): you have your CPU fan plugged into NO mobo port. Instead, it is plugged into a direct power connector from the PSU and it runs full speed all the time, OR you have it plugged into some separate fan speed controller. In either case, there is no way for the fan's speed pulse signal to get to the mobo CPU_FAN port so the mobo thinks that fan is not turning. So it is up to you to check that fan from time to time and ensure it is working. The mobo never will be able to check it. If this is your setup, you should go into BIOS Setup where the CPU Fan speed is checked and controlled, and tell it to Ignore the speed of the CPU Fan.
 
Jan 26, 2014
215
0
10,690
Thank you both for the very thorough answers! It turns out I just had the cpu fan plugged into the wrong port and my motherboard thought there was no cpu fan on. In return, my computer ramped every other fan in my case up to nearly full RPM in attempt to cool my cpu down. I fixed it and thank you for those very nice tips! I will keep those in mind and keep a sharp eye on my cpu fan to make sure it doesn't stop working. :)