Found why the radiator fan quit. Turns out that the plug-and-play harness connected the fan to a duty-cycle controlled output, one without a flyback diode. The electrical engineering speak means that if it’s not configured right, it’ll pulse on and off, drawing a near-constant arc across the contacts due to driving an inductive load. You can see how burnt and melted the relay is around the contacts. Going back and checking how the manufacturer configured it as part of their base tune, apparently the tuner changed the output configuration, resulting in one fried relay. After setting it back to the original configuration, it works fine now.
I have some video of some of the dyno pulls; I’ll post it up eventually. Too bad I missed a picture of the 3-foot flame that popped out when he let off after one of the pulls 🙂