Quote Originally Posted by NTFDAY View Post
I'm assuming you want to be able to manually override the temp sensor. The wire coming off the temp sensor should be providing a ground to the fan when the sensor is closed so you need to splice into that wire and run it to a spst switch on the dash. Then run a wire from the other post on the switch to ground. With the switch open the sensor controls when the fan comes on and with the switch closed it overrides the sensor.
That's a good one, never considered that before.