Temperature switch
 

Id like to add fan for my motor, just for safety, so that when it reaches some specific temperature fan goes on to cool motor and preventing it from overheating.
Or i could make it to show its temperature in leds green, yellow and red, red being overheating.
I have found one small circuit to make fan switch, it might be able to use for leds.
http://www.heatsink-guide.com/conten...=control.shtml

Has anyone else found something similiar, perhaps even smaller "device"?

There are several different ways to go about it. The thermistor is the best way, but you could use a small transistor as the temp sensor as well, it just isn't very linear.

A FET is probably the best way to do the actual switching, but you could get away with a smaller one as long as the drain-source current and voltage ratings are adequate. Since it is in switching mode, and not switching often, there is very little wasted heat because the only losses comes from the rdson value. Heck, a single ESC FET would be fine and small enough. The adjustment pot in the linked diagram could be a tiny PCB mount version.

You know the old rule, "kiss" keep it simple stupid (I'm not calling you stupid by the way). I just noticed you are from Finland. The "kiss" rule may not be known there like it is here in the US.
Why not just have the fan run all the time with no switch. It is much more simple that way. Unless you want the challenge?

i was gonna ask the same thing. i have my fan running all the time, motor likes it hehe

Its that challenge and that way i could know something about motor temperature, if its on its hot if its not its warm, without any tempgun.
Think it this way, you could add allmost anything to those output leads that temp switches on, it could be buzzer to inform you that motor is overheating or something like that.

You might want to rethink that.... If the motor is hot, the fan WOULD be on... but if you are close enough to the truck to see or hear that the fan is going, the motor would not be building any heat and the fan would stop.. your probably better off just gearing correctly and buying a temp gun.