Several months ago my 02 MCS's radiator fan seemed to be getting more sensitive and was coming on seconds after starting the car. The reserve tank had the correct amount of coolant, so coolant was ruled out. Finally one day the fan stayed on after I shut the car off, and it wouldn't shut off. I pulled the breaker and waited 30 minutes and plugged it back in, but it came on again. I then unhooked the positive cable on the battery thinking it might re-set the computer. 30 minutes later I reconnected the cable but unfortunately the fan came back on. Being that the car was completely cool, I ruled out the temperature sensor.

Looking under the bonnet (hood) I found a fan connection plug located on the right side of the radiator near the top I unplugged it and reconnected. It still came on. For no reason but frustration I plugged it in and out about 6 times and it finally shut off.

Now for the past month the fan has been cycling perfectly and cooling as designed. Problem resolved for now.

Although the connection didn't show any signs of corrosion, it must have been corroded I guess.

Hope this helps anyone if they experience this problem.