if youre wanting to mount a led in a visible location, heres how;
note..leds are 3-6 volt lights(depending on color), so make sure you buy a led designed for 12 volts (has a resister already installed)leds have a pos and neg terminal,test with a 9 volt batery,a led will only work wired one way unlike a glass type bulb.
1)hook positive side of led to a constant (battery)source fused at 1 amp.
2) hook the neg side of led to the power "in" side of the fan(s) relay(large red wire,not the small trigger wires)or you can pull the oem fuse,see which side DOES NOT have power when fuse is out,and connect to that side..
thats it, if the fuse blows for the fan relay, ground will "feed" back through the fan(s) when the relay closes ,energizing the led.