looks like reply didnt post so here it is again From the manual,lights when the Tail/Stoplight bulb is burned out. As for the Fan the sensors turn on range is anywhere from 80-102C for turn on, way to high for my taste. What I did was install a on/off switch with one side connected to the black wire going down to the thermal switch(located at bottem right side of radiator) and connected the other side to ground. So I can turn on the fan at any time. mounted the switch on the pastic part right in front of the gas tank, but it can be located anywhere.