After adding second system fan the first not working


Junior Member
Sep 6, 2008
Hi all.

I have assembled my PC with MB Gigabyte MA78G-DS3H approx 6 months ago. I installed only one system fan (back of case) plugged in SYS FAN1 on the MB. As far as I understood FAN1 connector offers RPM adjustment for the fan not to run on max RPM if not needed, while FAN2 connector always runs the fan at max.

This system fan has worked fine for me but in order to bring down the system temp I decided to install another one today. Also on the back of the case. I plugged the second fan in SYS FAN2.

After turning on the PC I noticed that the second fan runs on max rpm as expected, but the first one is not running at all. It is the same fan I used so far plugged at the same connector so I am sure the fan itself is OK.

The system temp reported both by BIOS and Everest is 72 celsius. On this particular board the system sensor is close to the integrated GPU (which I use) hence the rather high system temp.

But once I have two fans why would the first one not work? Can the system consider these 72 degrees "normal" and using the regulation not turn on the fan at all?

Any ideas what to do on this board to bring the system temp down without actually removing the board to replace the heatsink on the graphics chip?

I don't play games and that's why I am just using the integrated graphics, just regular use. 72 degrees is not the end of the world but I am confused why the first fan is not working now and in addition if there are any advices to cool down the system temp without investing lot of money I would like to bring down those 72 at least a little bit.

Another interesting note, while both the BIOS and Everest were showing these 72 degrees I touched the graphics heatsink and was able to hold my finger on it without any problem. I never thought I could touch 72 degrees that comfortably. But both Everest and BIOS reporting same temp so I got no reason to think it is wrong reading. Any thoughts? Could this be wrong reading and that's why the first fan is not turning on at all? But if the MB "thinks" those 72 degrees are real it would turn the fan on even if the reading itself is wrong, wouldn't it?

Any help is appreciated. Thanks.

EDIT: I sorted it out. It turns out while mounting the second fan I pressed it too hard to the bottom of the first one that the fan actually could not rotate. Moved the second fan to the side of the case now and everything looks fine. Cheers.