ok , i dont believe fuse 13 draws 40amps, sorry.did you use an ammeter, and if not an ampclamp meter this is harder.here is a page that shows all ways to find phantom drains.
http://www.fixkick.com/drain/drain.html12x40 is near 500 watts, no way, if you had drain link thatthere would be 1: huge light.2: huge heat3: or huge noise.for sure. 500watts dont just fly way like a bird, not in this world.no lie we can find, it, but first tell what tools you have.really.