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The temperature sender (the sensor that sends the temperature signal to the gauge) has to be immersed in coolant in order to correctly read the temperature. If the coolant is so low that it leaves the sender high and dry, the temperature shown on the gauge will not be a true reading. if the sensor is not immersed in the coolant, there a big chance it wont read at all...
The engine coolant temperature sensor and coolant temperature gauge sender are located on the passenger's side of the engine, under the intake manifold.
The temperature sensor (sends coolant temp to the PCM) is located in the top of the thermostat housing. The temperature sender (sends coolant temp to the gauge) is located in the bottom front of the same housing.
1990 Chevrolet Lumina temperature sender is located on the back side of the thermostat housing. The sender has a wire that goes to the temperature gauge.
Thermostat is the part which functions to maintain engine coolant temperature by restricting the flow ( open and close based on the coolant temperature ) to the heat exchanger ( radiator). Water temperature sender ( water temperature transducer ) is the one which signals the the water temperature gauge. so water temperature sender may not work and show the same value on the gauge. but engine temperature will rise and vary depending on the load. the engine will be cold when you start the engine after an overnight and if you touch some safe parts of the engine you will feel the temperature rise even if the gauge does not indicate it. hope this will help you. thank you.
engine coolant
Check the wire to the sensor and be sure it is hooked up. If so remove it from the sending unit. Turn the ignition and have someone watch the gauge while you ground it to the engine. If it moves the sender is bad.
There are several reasons this could be:There is no coolant in the engine to trigger the temperature gauge, this will cause complete engine failure very quicklyThe gauge, wiring or sender are badThe engine temperature control thermostat has jammed open or it has been removed.
only 3 reasons a temp gauge wont work the temp sender is bad the gauge is bad or the wire from temp sender to gauge is broken
Bad gauge or defective coolant temperature sensor
water temperature. 180-220 degrees
Low Coolant or faulty gauge