Could you use an old mechanical (bulb type) coolant temp switch in the inlet of an intercooler to switch on an IC fan? And I wonder if you can adjust it down far enough? What temperature would you switch at, 40C? Or are there any suitable electronic gizmos out there to do this?

this isnt exactly about fan switches, but it covers electronically controlling intercooling sprays which is not too different, lots the the stuff they cover is pretty relevant

http://www.autospeed.com/cms/article.html?&A=0527