91 mustang lx cooling fan cycles

91 mustang with 4cyl, cooling fan and ac compressor cycle on and off every minute or two, engine temp stays way low, ambient temp is around 40 degrees fahrenheit, has new thermostat, am suspecting the constant control relay that controls the ac clutch and the cooling fan, I think it is under the drivers dash, but am not sure, any help or ideas would be appreciated. thanks in advance.