Mount a fan on the Rpi3

[iAlle]

Hi my rpi3 have overheating problems so i have to mount a fan, i've mounted it and connected it to gpio pins 4 and 6 but how i activate it?

[JimmyN]

If you've connected it to board pins #4 (5V) and #6 (GND) it should run as soon as power is connected to the RPi. Provided the fan will run on 5V, some 12V fans may not start up unless you give them a manual "push" to get started.

Board pin #4 is the 5V rail and not an actual I/O pin. It can't be switched on/off, it's powered whenever the RPi is powered.

If you've actually connected it to GPIO4 (board pin #7) that is an IO pin and won't provide enough power to run a fan. You could use it to switch a transistor that would turn the fan on/off.

[Rive]

If you are using a connector for GPIO header pins 4 and 6 on the 5V rail you may need to switch the wires around (push tab with like a small flat head, or even toothpick, pull out and reverse, push back in).

I think it is red (+) on 4 (5V), and blk (-) on 6 ground. If wires are not color coded, do trial and error till you get it right.

I had to switch the wires around on mine for 5v rail in any event for my 12v fan.

[iAlle]

thank you guys, switching wires worked fine, and now is working good. i tested it for 10mins and no overheat problems... thanks so much!

[Rive]

thank you guys, switching wires worked fine, and now is working good. i tested it for 10mins and no overheat problems... thanks so much!

Run Stress and Cpuburn to see if 100% core usage puts you into overheat or throttling. If it does, you may want to provide more ventilation/air movement, and/or get a better case (or as was the situation in my case, get a better/bigger heatsink).

for how to test, see: viewtopic.php?p=952371#p952371