i replaced the fan motor the sensor in the radiator and it still doesnt' cut on. i even turn the a/c on but that fan didn't cut on either. what could it be

try looking at the relays just in front of the battery (between the battery and the front of the car) and make sure those relays are working properly

If you don't mind ghetto style hook your fan to a toggle switch. Just switch it on in traffic or when the gauge is 1/4 of the way up. Just don't let your girlfriend drive it.

oh and try this http://www.redpepperracing.com/technical
In the service manual you can find step by step troubleshooting for that radiator problem. Good luck!!

relay switch, thermostat, and check all wiring