Rad. Fan not working

The car was overheating and I found the fan was not working. I changed the temp. sensor and checked teh fan. I assume I need to change the fan switch. Does anyone know where it is located on a '91 3.1L?

The fan switch is just behind the T-stat housing on the drivers side of the motor. There is a relay also, between the battery and the washer solvent bottle mounted to the fender. I would try the relay first, easier to change, cheap, and you don't need to open the cooling system to change it.