[Pazuzu]

Originally Posted by A930Rocket

Thanks, Pazuzu.
I was going to use the factory wiring and fuse, as it’s heavy wire powering the fan, and hook it up to the relay. From there to the fan. Negative wire run to the switch.

That'll work

If I go with all new wiring, there is a positive lug for jumpstarting the car in the engine compartment. Can I use that for both high power to the fan and low power to the relay, with the negative wire running from the relay to the switch? Both power wires would be fused.

That should work

Originally Posted by RANDY P

I use this on my 89 Silverado along with an AC Delco aux fan. Been 3 summers so far in AZ, no problems, works like a champ. Hayden 3651. Lives underhood.
https://www.amazon.com/Hayden-Automotive-3651-Adjustable-Thermostatic/dp/B000C39C72

But this is a better answer. If you put the fan on a switch, the day will come when you're distracted or whatever and don't trip the switch by hand. Then things go poorly. Let an aftermarket thermostatic do the work for you.