1991 Acura Integra Radiator Fan Switch

It is located Under hood, driver side, front engine area, rear of cylinder head, mounted in engine block also here is how to test remove and install
TESTING
Disconnect the electrical connector from the cooling fan motor.
Test the cooling fan motor operation by connecting 12 volts source to terminal A (top) and negative to terminal B (bottom).
If the motor fails to run or run smoothly, replace it.
REMOVAL & INSTALLATION
Disconnect the negative battery cable. Disconnect the electrical connection at the cooling fan motor.
Remove all cooling fan wire retaining clips.
Remove the radiator fan shroud retaining bolts and remove the shroud assembly from the vehicle.
Remove the cooling fan mounting nuts and remove the cooling fan from the shroud.
On some vehicles there may be enough clearance to remove the cooling fan motor from the vehicle without removing the fan shroud.
To install, reverse the removal procedure.

Yes, the sensor is either in the therostat housing where the upper radiator hose attaches to the engine or on the radiator itself. There is also a relay that is switched on and off by the sensor.