Temperature gauge My car recently started giving me a problem that when the radiator fans turn on the temperature guage goes all the way to hot. when the fans turn of the gauge goes all the way down.

Lack of prestone

Try disconnecting the sensor. then turn on the ignition switch and see what the guage dose. If it still goes to the top, chances are there is a short in the wiring. If it does nothing, chances are you have a defective sensor.

The powertrain computer turns the fans on through the cooling fan relays, based on information from the coolant temperature sensor. The fans will only come on when the coolant temp. is pretty high-varies by manufacturer, but it is over 200 degrees, some as much as 230 degrees. So the fans will not come on when engine is started, but they should come on before the engine overheats. You should have them checked. Also find out if the temp. gauge sending unit is separate and different from the coolant temperature sensor-on most cars, they are separate, maybe not on yours?
Free advice from a shadetree-not worth a lot, eh? lol.

Yes, the temperature gauge should normally stop in the middle, between the cold and hot points on the gauge. When the engine is cold the thermostat will be closed and will keep recirculating the coolant in the engine block until it warms up sufficiently. Then the temperature of the warm coolant will cause the thermostat to open the channel to the radiator to get rid of excess heat, which should stop the coolant from over heating. So the effect of the thermostat keeps the coolant at a fairly stable temperature. When the coolant runs low, it can't transfer enough heat to the radiator and the coolant and engine then over heats. Watch for radiator leaks under your car after you have been driving it. If the coolant goes low again fairly quickly you could have a leak in a hose or the radiator itself.

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----

temp gauge goes erratic? http://technoanswers.blogspot.com/2012/01/heater-blows-intermittently-and-temp.html

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Temperature gauge keeps fluctuating up and down close to red? http://technoanswers.blogspot.com/2012/01/temperature-gauge-keeps-fluctuating-up.html

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Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
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Temperature gauge does not move and no heat when heater is ON? http://technoanswers.blogspot.com/2012/01/temperature-gauge-does-not-move-and-no.html

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This details will help.Thanks.

Since you just replaced the thermostat and it still over heats there is a good chance you have air in your cooling system. You can find step buy step instructions on my tip and how to page. Feel free to take a look.

FLUSH RADIATOR, HEATER CORE AND ENGINE BLOCK.ADD 50 / 50 ANTIFREEZE AND WATER ALSO REPLACE RADIATOR PRESSURE CAP.IF TEMPERATURE GAUGE STILL STAY HIGH THE ENGINE COOLANT TEMPERATURE SENSOR COULD BE FAULTY.

Check to see if the fans are operational, anything below 35 MPH the fans cool the radiator, anything above is cooled by air passing thru rad.

Very correct the ECT is a 2 wire thermistor,when coolant temp increases, the resistance andsignal voltage decrease,If you disconnect the sensor the fan goes on, you just trouble shooted the vehicle cooling fan switch, If anything the signal to the gauge itself may be non-op and not getting to the indicator, try this with vehicle at warm up temperature if you turn the A/C does the fan turn on.it should if it doesnt the power juction box (fuse and relay in engine compartment should be checked, for any opeen fuses, By the way the guage information is from the PCM

The thermostat may be wearing out. A thermostat controls the engine temperature to keep it at a consistent temperature, The other fan will probably turn on if you turn on your Air Conditioner.