Probably the AC switch at this point . Mine failed and the fan was on 100% of the time, I deleted the AC and now my fan runs all the time. I don`t really mind since these engines tend to run hot anyway. You could add a manual switch inside but there`s always the risk of forgeting about it and letting the car over heat. I`ve been driving the car with the fan always on for the past 2 years, not a single issue, in the winter when its -25C or colder the engine doesn`t run at the prefered thermostat temp but I still have heat and the afr is steady 14.7 so it doesn`t run lean or rich.