By the way, a typical 40/50A automotive relay will *not* power that fan reliably. I tried. I even tried two in parallel. Nope. They both failed and had me cutting and twisting wires together on the road...
This relay, however, has lasted over 60K miles in my truck switching on and off the high circuit on the fan only.
https://www.amazon.com/TE-BOSCH-Curr...osch+75A+relay
Additionally, you want to run at least 12ga wire to the fan. I originally ran 14ga wire and found that there was a 2volt drop at the fan when the fan was running, and the wires would get warm. I ran 10ga and the fan ran noticeably faster with much less drop.