Fan - hook to constant or ignition "run"

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May 11, 2007
Any thoughts on what's best - connecting the electric fan to a 12 volt constant or the run position on the ignition. Do I want to fan to run run continuously when the engine is hot even when the ignition is off? Or just turn off when I turn the truck off?

Also, any compelling reason to install a switch to turn the fan off manually?

I have a Taurus fan and a Delta Current Controller for my fan. My Delta controller is wired directly to my battery but the power is controlled by a wire from the Delta controller to the ignition. So in essence my controller always has power but is cut on and off by the ignition wire. This way the Delta controller has the benefit of large power cables coming directly from the battery. I would also suggest the manual switch. It is really convenient to shut off the fan while in deep mud or water. This way your fan doesn't become a large propeller spraying your motor with water. Delta has an optional led that I also wired into my dash so i always know what my fan is doing and how fast it is running. Go to Delta Current Control and read up on the controller. It is the absolute best way to go with the less wear on your electrical system. You can make a crappy system from the local auto parts / hardware stores but it is not the best way. I have $5,200 in my motor and I wouldn't take the chance of locking it up.
You aren't circulating coolant when the engine is off, so running the fan won't do much except cool whats in the radiator.


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