Not completely familiar with your particular car, but 99% of the cars I've worked on the fan sensor was not actually in the rad, it was in the thermostat housing, which is where the upper rad hose attatches to the engine. It will be an aluminium "bubble" with the rad hose nipple, between one and several vacuum fittings, and between one and several sensors coming out of it. One of them will be your fan sensor.