So, the fan's activated by a temp switch, not a pressure switch? Also, would it be possible to confirm the temp that the switch turns the fan on at?

I thought about just making it so the fan would be on at all times, but at higher vehicle speeds, I don't think it's really necessary, and why put unnecessary wear on the fan?

Going off somewhat on a tangent I just took a look at my car for the 212° sensor that was just mentioned. Where, exactly, is it located? I've got a sensor with a black wire leading to a black circular plug attached to it in the area that was described, right by the hose connection on the block for the upper radiator hose, maybe 1/2" from the valve cover. I've got 12 volts at the plug with the key on (car not running), and with a cold engine, the sensor does not complete a ground. I attempted to jump the plug to ground, and from the best I can tell, nothing happened. The fan didn't come on, I didn't hear anything click or anything, and the temp gauge stayed at the lower peg.

FWIW, a friend of mine has an '84 300D (federal car) and i believe he has the same plug/sensor setup; when I first saw it, I thought it was the sensor for the water temp gauge.

My fan doesn't come on at 100°C, although I would like to set it up so it does...

Thanks!