electric fan

An electric fan, 10G wiring, fuse, a Bosch 75A relay and a on/off switch.


Or you could go with a temp switch or a DC fan controller.


There is no set parts list, you have a lot of options here.
 
The guys are right - there are myriad options. If you provided more info about your set-up and desires, that can help tailor suggestions.
E.g., is this a DD? Do you mind flipping switches or do you like to not worry about it? Etc etc............

Good luck.
 
You will need some electrical skills to do the job right.

Here's a simple non adjustable fan controller that you can build if you do have the needed electrical skills.
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My advice from experience: spend a few dollars more, get something along the lines of a 94/95 fan, and splurge for the DCC. It's the easiest setup and very reliable. I went the relay route, and was generally unhappy (I won't get into details, the story is waaaay too long). Since using the DCC, all is good. If you do a search, you'll see about a thousand threads on this.