Is it OK to just use a in-line * fuse (10 gauge wire), between a 30 or 40 amp toggle switch and the fan, and wire from the fuse block to the other side of the toggle switch. Of course the fan will be grounded. -- * What size fuse ? --- I'm trying to avoid a controller. -- Thanks

 

All sounds good to me..30AMP should be fine on the fuse... But I would feel better if you used a Bosch relay Also.

Something like this: Note, this is lighting, but same principles apply...

https://www.google.com/search?q=bosc...9JniwXaFFAM%3D

 

I've run a toggle switch straight to my aux fan in my XJ for a long time. It gets a little warm when run for a full day of wheeling so I am installing a 40 amp relay kit for a led light bar. Will still have functionality of a toggle switch to leave running during long idle times and ability to shut off for deep water crossings. Not sure what amps your fan runs but a relay installed with switch would be better. Here is what I am using