Extra fan

[clue144]

I have two fans connected and i would like to connect one more but there is no place on the mainboard, how do you do then? Please see attached image

[FDM to SLA]

Depends on the power draw of the new fan. If its low and the board can handle it then piggy back of a fan that runs when you want the new one
to run.

I took a feed from the power supply on my CTC printer and added a DC-DC voltage dropper, you can get these with variable control with a knob.
Very cheap on ebay.

I can switch the fan on independantly of any other fan and can vary its speed to barely turning to blowing the part off the build plate. (Slight
exageration maybe) But its adjustable.

Look for DC-DC converter on ebay or buck converter / voltage dropper.