Messed up temperature reading when using chassis fan 2 connector

Duje Lalic

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Mar 2, 2014
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4,510
I've just bougth an ASUS Z87-A mbo and I'm experimenting a bit with chassis fan configurations. What I spoted is whenever I connect a fan to CHA_FAN2 connector on the motherboard and go into BIOS to check temperatures I see a 5 degree celsius higher motherboard temperature then when nothing is connected on that connector. It does not matter how the fan is placed I even tried leaving it out of the case.

So the problem seems that just the fan drawing power from that connector has influence on temperature readings.

Is my motherboard faulty? Everything else seems to function perfectly fine. I connected all the fans now via other fan connectors and even the temperatures are now normal. So it seems I just have to avoid pluging fans into that fan connector. But it bothers me because it is a new board....

Did anyone else have any similar experience?
 

Duje Lalic

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Mar 2, 2014
3
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4,510


Umm, I don't have any additional chassis temperature sensors. There are two temperatures that I see inside the BIOS: CPU temperature (shows same values regardless of connected chassis fans) and MB temperature. That MB temperature is I suppose a temperature sensors somewhere on the motherboard.... And If nothing is connected on CHA_FAN2, but is on other CHA_FAN connectors I see temperatures around 25 degrees C. If however I connect a fan to CHA_FAN2. MB temperature shows 30 degrees C.
 

Duje Lalic

Reputable
Mar 2, 2014
3
0
4,510


I have 3 optional chassis fans that I have installed in the chassis ...

I have 3 CHA_FAN connectors on the motherboard.
CHA_FAN1
CHA_FAN2
CHA_FAN3

So I connected my fans to those connectors ... I spotted that when I have CHA_FAN2 connected, the temperature that the motherboard reports as MB temperature is 5 degrees higher. I first thought that was because that particular fan was causing such an air flow in the case that it reduces the cooling effect of other fans. So I disconnected it and as soon as I booted up in BIOS the temperature was 5 degrees lower... I was a bit suspicious right then because the system could not have cooled off so quickly.. I tried connecting the fan back but leaving it out of the case completely. The temperature went back up by 5 degrees. That tells me that something is wrong with the temperature sensor on the motherboard... I also tried different kind of fans and it behaves the same.

I only wish to know if this is at least somewhat normal... That it is known case or something...