Cooling Fan

My cooling fan, the one on the passenger side of the radiator, is always on, everytime i stop my car, i can hear its always on, 24/7(well, when ever the car is on). I unplugged it, when i was running some idle tests, and i forgot to plug it back in, but my engine temp never rose higher than normal. does the other fan come on ever, because i have numerously stopped my car, and opened the hood, to find the tranny side fan going, but the motor side on stopped. Any ideas whats up?

i think that other fan is the condenser fan and comes on when the air conditioning is being used, can't remember why i think that, but i believe thats why. never seen mine on either...