I installed 3 new fans on my case. I already had 2, so now I have a total of 5 (1 CPU fan + 4 case fans). My motherboard only has 3x 4-pin connectors so I bought PWM fans that can be daisy chained. The CPU fans is not daisy chained and is connected directly to the motherboard's CPU fan connector. The motherboard is ASUS P8Z68-V LE.

After connecting everything, I turned on my computer and had a BIOS error: CPU fan not working. However, I clearly see the 5 fans spinning inside my computer. Since my CPU fan is spinning I disabled that check in the BIOS and was able to get in Windows.

In CPU HWMonitor, it shows CPUFANIN at 0 RPM when doing nothing. When I run a FurMark 1080 test, I see the RPM raising between 500 and 800. Temperatures are good during all the test, never going above 50C. Once the test is done, the CPUFANIN goes crazy and raise between 18000 and 61000! When the CPU cools down to about 30C, the RPM goes back to 0. Those values doesn't make sense.

My questions are:

  1. Should I worry about this? I don't really like that I had to disable a check in my BIOS.
  2. Why is the CPU fan RPM reading now wrong? I didn't change anything on the CPU fan.

Update 1: I realised that my CHA_FAN connector was still free on my motherboard, so right now my fans are connected like this:

  1. 1x CPU fan is on PWR_FAN
  2. 1x fan on CHA_FAN
  3. 1x fan on CPU_FAN1 (HWMonitor shows this one as AUX1)
  4. 1x fan on CPU_FAN2 (HWMonitor shows this one as AUX2)
  5. 1x fan on molex connector

No more daisy chaining, but the problem is still there. All fans are spinning. I'm going to do more stress test on my machine tonight and if temperatures are good, I'll stay like that.

  • 4
    I’m not sure why the motherboard is misreporting the CPU fan speed but it’s likely related to the fact you can’t daisy chain fans plugged in to your motherboard. One wire is an RPM sense wire and if you tie multiple fans together you’re going to get off the wall crazy results. If you want to run more fans than you have mb ports for then connect them to a standard molex plug from your power supply. You can daisy chain as many as you want from there, but not from your motherboard. It’s not technically called “daisy chaining” because they are hooked up in parallel not in series. – Appleoddity Dec 13 '17 at 2:10
  • Oh thanks, I updated my question. – Simon Arsenault Dec 13 '17 at 12:28

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