89 240sx ka24 cooling fan problem

[GatorbackBob]

My coolant will boil over into the resevior bottle after shutoff, but my temp gauge doesnt read high, after opening the hood, and turning on the a/c, I noticed my cooling fan wasnt kicking in, so I disconnected the pigtail, and ran a hot lead from the battery, the fan kicks right in, I figure it is the temp control that screws in the bottom hose inlet, autozone ordered the only one they had for this car, and the pigtail was way too big, the sensor threaded right in, so short on time, I decided to get junior electrician on it, and cut&splice the wires from my old plug to the new sensor, but the fan still wont kick on, my ? is if I just lead that hot wire to a grounded toggle switch in the cabin, and manually turn the fan on/off, will this cause future problems because I am not using the proper sensors, etc.?BOB