The fan works on a neg ground from the oil temp sensor . When the temp is cool the senser is open , IE no fan. When the oil increases with temp the resistance of the switch is less, till it completely closesand grounds to the engine, IE fan is on. I am currently running a 240CFM fan on my oil cooler that is connected to my engine fan . To correctly wire in a switch so both manual switch on starts the fan and if switch is off the sensor starts the fan you just need to splice the fan grounding wire ta a switch , and switch connected to earth ground. Very easy . Get a manual off ebay so you have the schematic. Works fine . No issues at all . I have also rewired my lights so all 3 lo & hi beam, and head light assist are manually controlled. IE I can run with just the display and select what lights I want on .