So apparently this is how I will need to wire the fan so that it will stay on until the engine is cool even after the car is off. So how would I go about adding a switch to this inside the car to toggle between auto and on?

 

Option 1:
Put a switch after the fuse before the control side of the relay/thermostat side/terminal 85.

Option 2:
Put the switch after the thermostat and then run the out wire to the nearest grounding point.

 

If you don't want the fan to run after shutdown, you can connect a wire thats
only hot when the ignition is on to the 85 connection on the relay. Usually
the one that goes to the coils will work.

Otherwise do what DarrenTRS says for a manual switch.

 

I just let the fan run until the coolant in the rad gets below the temp setting on the controller. Usually only takes 5 minutes or so, so it's not going to kill the battery.

 

If its 100 F outside it can take a lot longer than that. Ask me how I know

 

Yeah I think I'm just gonna wire it so that the fan only kicks on if the ignition is on and just make sure she's nice and cool before I turn her off. Now if I run a constant 12v to a switch in the car and from there to the + side of the fan that should give me the option to toggle between auto and on right?

 

I don't see where you would get any advantage at all by running the fan after shutdown.

Joe, I bought a 17 dollar adjustable fan controller from Autozone. Took a couple of hours of fiddling with the adjustment until I got it just right, but it's been running fine for years now.



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