[LeesTruk]

It's stand alone. Pictured alongside the controller is the brass tube/fitting and the sensor that screws into the fitting. This assembly is placed into the lower radiator hose and feeds the coolant temp. to the controller, which then determines how fast/slow the fans need to spin. If you go to Autocoolguy.com you can see more info on this controller and others that are available. Also, you can email Daryll and he will get back to you with any questions you need answered