1997 sentra cooling tempreture sensor problem.

There are two different thermostats--one in the cooling system, and one just to turn on fans. The AC has a separate circuit to turn on fans regardless of engine temp, so tind the the fan thermostat and test it.

temp sensor

Three thing you need to be concerned when the cooling fan fails to turn on, the fan, the fan relay, the coolant temp sensor, First the relay,go to the engine junction fuse and relay box there listed next to thethe ABS relay heater blower relay is the cooling fan relay, Now make a tool from the cooling fan relay,take the cover apart and expose the relay,when you collapse this relay the fan turns on stick in back in the socket key on engine off collapse the relay the fan should turn on if the fan doesnt turn on a fan is the solution if the fan turns on the coolant temp sensor will be the solution this sensor is located at the thermostat housing just follow the top radiator hose,you will see a sensor there

I think the problem might with the radiator sensor switch. Check the fuses. If necessary you can replace your radiator fan at http://www.buyautoparts.com/radiator-fan.html

Check the radiator and the cooling fan. open the hood as the engine temperature rises does the fan come on. if not that the problem, Also do this As the car is warming up(from a cold start) near operating temperature, turn off the car, watch out for the fan, engine of key in your pocket fell the radiator is there any hot or cold spot? if there is the radiator is plugged. Also if the radiator isnt plugged new doesnt mean it works, the water pump itself can be faulty. and dont forget the most important device the Thermostat you did timing belt waterpump they should of done thermostat.

which switch did you change? maybe you changed the switch for the gauge and not the switch for the computer

try turning key on with out starting see if electric cooling fan comes on if not start engine turn on ac if it doesn't come on that's most likely the problem (fan,wire or sensor to the fan )

THE COOLIG FAN RELAY MAY BE STUCK,PULL IT OUT AND THE FAN SHOULD QUIT.THE TEMPERATURE SENSOR COULD ALSO CAUSE THIS UNPLUG IT,FAN SHOULD QUIT.IF NONE OF THIS WORKS THEN HAVE THE WIREING CHECKED.

No, it should only turn on when the temperature switch tells it to. On a hot day you may hear it running even after shutting off the engine. The fan is set up so that when you are moving at enough speed the fan shuts off to save energy, when you slow down or stop the fan should come on to maintain airflow. If you check it at this point yes it should be running. When you start it cold the fan will not turn on for maybe 10 or more seconds when the engine starts to warm up. Hope this helps.

Things to be concered about; 1.) the fan never seems to turn on. This will cause your engine to overheat when you stop.
2.) Your heat is not working. The heat going away can be a sign that you antifreeze is low and that you are about to overheat.

One of the common things that gets missed at times is the radiator is down in cooling antifreeze. The car will act as normal during the warm up cycle and then the temperature guage will rise and then it will slowly come back down as the thermostat opens and/or the electric cooling fans come on. In actuality the engine is overheating, but it is not boiling over. The level of abtifreeze is at just the right level of lowness that you experience this phenomenon. After the engine cools off , (DO NOT REMOVE WHEN HOT - YOU CAN GET SCALDED WITH BOILING WATER/ANTIFREEZE)), remove the radiator cap and check the level within the radiator and also the antifreeze reservoir level. You can buy a 50-50 mix of antifreeze and water that is ready to put into the radiator. If the level in both the radiator and reservoir are correct, you may have a bad thermostat or some other problem.
Bob - 2003 Nissan Sentra SE-R SPEC V