There are people waaay smarter than me responding to this post, if I'm wrong maybe someone will correct me... but a method I have used to chase shorts is to disconnect the positive battery terminal and hook the test light clamp to the cable then touch the positive post with the test light probe (with the key off, doors shut, trunk shut, in other words, anything that would draw power has to be de-energized) if the test light illuminates you still have a short somewhere, for fused shorts I remove fuses one at a time until the test light no longer illuminates, thus at least isolating the system with the short, in your case I would leave the positive cable disconnected and hook up the wires in the engine compartment, hook the test light clamp to the positive cable then touch the positive post of the battery with the test light probe if it illuminates you still have a short, then one at a time disconnect the wires you just connected in the engine compartment until the test light goes out. Hope this helps.