What Stump said, you gotta dead short. tell him not to check his progress by producing sparks. Unhook the battery/grab his meter & start checking specific sections of the harness(es) to find out which positive circuit has continuity to ground. ANY ground is good & keep moveing the red probe till you find the wire/terminal/connection that shows near zero ohms on low scale. Always a good idea to unhook the battery BEFORE switching the scale to ohms.
live every 24 hour block of time like it's your last day on earth