I bought the car like that and guy told me that the gadge wasn't working so when summer came around the temp would go up alil which I realized the fan was always spinning even when it's cold I checked it wasn't connected to the tempture sensor and had direct power from the battery I connected it the right way and replaced the sensor but car over heats and the fan never comes on I wanna know what is the problem that it's over heating

 

Test the circuit by unplugging the thermo switch and jumping the plug. The fan should start when you turn the key on, If that works either the thermo switch is bad (just because its new doesn't mean it is good) or the plug is bad not making contact.