I usually put mine in the intake, as close to the thermostat as there is a pipe fitting. You can use a Tee fitting, sitting flat, to accomodate your original temp sender plus the sensor for the electric fan. But Gerry's way is better, if you have a thermostat housing with a pipe fitting in it. Only downside there is if the thermostat sticks shut, you won't see an accurate temp at the sensor. Of course, with no flow through the radiator, what good would the fans do LOL!