The reason you want it HOT, is that batteries and elecctronics don't like heat, so when you turn it up, the solder melts fast and the tip is only on the parts a minimal time. If it doesn't flow right away, and the tip is hot, make sure its clean and the solder is new. Also, you don't want the joint to be a "cold" solder, but rather have the sodler flow and make a strong joint. Hako all the way.
RC Car Action Editor and Photographer